question about reusing yeast, for the same batch?

briefeing:
so i had a black ipa fermenting away. i wanted to dry hop it, this was last wednesday, and only god knows why, i decided to pitch to secondary and throw in my hop pellets, only at 3 days of fermentation.

well the next day it was a mess and wort was making its way out of the carboy, so I took off stopper and airlock, had a 4" long tube of hop mass pop out of the top, so i just decided to sanitize stopper and airlock and put it back on.

Now I have a feeling it didn't ferment all the way, since I took it off primary at only 3 days. (what was I thinking?) tonight I plan on taking a gravity reading, and expecting it to be way unfinished, I'm wondering if I can pitch back into my primary bucket. I saved the yeast cake in primary bucket since I was planning on pitching my next brew on it, I put a lid on it so it's been air tight and in the fermentation fridge at 65 deg.

i know it's all kinds of room for an infection, but what are my options if my beer still has lots of fermentable sugar left?

 

Your options? Many but you have some misconceptions here. In 3 days it's doubtful you have a yeast cake during fermentation of your ale, all of your yeast (that you care about) is still is suspension, you simply have trub.

You also didn't take it "off" primary, you took it out of primary, you have simply moved it to a secondary fermentation bucket.

My recommendation: leave it in secondary and dump that trub from your primary bucket. If it doesn't ferment out then I'd pitch more yeast but only after verifying with a hydrometer in a week. Once it's done fermentation, then dry-hop it as the ongoing fermentation probably knocked out what you were wanting.

Good luck.

 

My thought would be to just leave it and hook up a blowoff tube. There was probably more than enough yeast in suspension when you racked to finish the fermentation, and racking back and forth is just going to be unnecessary risk.