I don't think your 3lbs is a screw-up! It could just be water retention from salt, hormones, anything!
We all have times like you do and as long as we get back on track, we are winning the battle.
The best thing that you did was come here and ask for help. We might not have the answers but we are here to pull you through.
When I think (or do) go off track whether it's with food or mentally, 3FC has been my saving grace. It's like you are all my teammates and we are winning this game! I read about other's struggles, I read the NSV threads, I read and look at the mini-goal pictures.
I don't know if any of the things that work for me might help you but I wanted to post so you know you aren't alone.
Edited to add: Before I forgot to note-----you are down 26lbs!!! Let's not forget to celebrate that too!!