I had something similarly weird (although not excatly similar) happen about a month ago:
I was throwing my Avalanche with no problems. I threw a strong sleeper and all of a sudden it was rolling across the (luckily carpeted) floor. I figured “oh, the loop must have snapped at the bottom.” Nope. String was fine. In fact, I put it back on and continued throwing. The only thing I can figure is that my tension was really loose and somehow my yoyo popped out of the loop.
I think you’re onto something FiveIronBrian, but there’s the issue of it going all the way through while attached to my finger. I just replicated the slipknot-y nature of it you were explaining but it wasn’t attached to my attached to my finger.
Try getting the slipknot end of the string thru the twist while it’s attached to your finger. Theoretically your whole body would have to go through the twist to get my result.
Maybe it was what you explained and i somehow pulled it through after taking it off my finger but before noticing what happened? Doubting that as i noticed while it was still attached to my finger… But it is the first logical explanation
You’re not quite getting it. You can do it with the slipknot attached to the finger. Open part of the string by untwisting it somewhere between the yo-yo and your finger (say, the middle). Now take any part of the string between your finger and the opening you created, and push that loop through the opening. Then just pull that loop through and tighten everything up. It becomes “once-through”, kinda like how you pass a loop through the slipknot, but then when you tighten it, the string only goes through once. See it?
I follow you all the way to “tighten everything up”. Can you make a video please?? I gibs FHZ to first person to convince me they’re right with a video
Also, everyone ignore me asking how the yoyo went through the twist, it was late last night and clearly the other end went through the twist.
If you’re saying pull a loop through the twist and keep pulling till the slipknot is through the twist and then once you take it off your finger it would have my result…i get that… But there’s some weird issues with that I’ll explain later.
Jk brian you’re right. I just did it. You want free fhz?
Ahh. This was driving me nuts. Now I get it.
I’ve seen a few bizarre outcomes in yo-yoing, but this one took the cake. Glad the mystery is solved. You can keep your FHZ, it’s cool (though I’ve never played one). I’m happy to just help out.
You should post a tutorial on your new “trick”. 
It would be like the washing machine!
I can’t replicate it mid trick but i can manipulate a string to get the result.
I know how it’s done, but i don’t fully understand how the string does it yet. Need to do it slowly and carefully later to see what happens when you tighten the string to see exactly what happens.
nvm just did it… Stupid easy and simple! Thanks!!!
I have had that happen to me a few times. I didn’t think much of it. Got rid of it and kept throwing, haha.
It’s happened to me before also
This happened to me when doing kimmit sandwich! Maybe its just some tricks make that happen if you bind wrong or something.
I’m thinking you did it when you put on the string?
Have you guys heard about the swivel trick?
I think you just the entire yoyo.
That happened to me once. I got it, and was so baffled, that I showed my dad. My dad and I just sat there staring at for a while, keeping it loose, so when we figured it out, we could get it out. I think it was me, but I turned around really fast or something, and knocked it off what it was on. When I picked it back up, it had tightened, and the whole knot was gone. It was the weirdest thing that’s happened to me in yoyoing yet…
Got the smallest fishing swivel I could find at Walmart yesterday for like a buck. Put it on the string as close to my finger as I could get it… has about a cm between my finger and the swivel.
Doesn’t interfere with play at all, don’t even notice it to be honest, it’s so small and close to my finger, you never really put your nonthrowhand there.
String Tension = Perfect for days. I think this piece of string is going to last me quite a while lol.
I know adding a swivel is probably “lame”… but in these day and age, we’re using $160+ precision ball bearing yoyo’s, adding a swivel isn’t taking away from the heart of yoyo’ing that much. I mean it is, and it feels like a “cheat” and I miss managing my string tension… but for some hardcore sessions where I don’t wanna deal with tension… yup… gonna be using this thing.
Hey I did that a few years back. Worked fine, but I never really trusted it not to break and replacing string was a pain since I don’t cut my 1A string. I think it also interfered with the yo-yo walls when wound up. Maybe I’ll try it again sometime; I didn’t have many low-walled yo-yos back then.
Yeah I made some pretty nifty/tight knots then burned the ends that I cut… you know the deal. Hasn’t failed me yet, kind of scary though.
I was thinking of adding a drop of super glue to each knot.
Ah, I never thought of melting the polyester. Sounds like a hassle to me 
I was ok trusting the knots, I didn’t trust the swivel.