So this is something that happened quite a while ago, but I think it's worth mentioning.
I went to New York this year and had a bit of an up and down time. After spending THREE HOURS in what was a pretty short queue I was desperate to simply get to where we were kipping for the night. My girlfriend who had been waiting for me the whole time without a clue what was going on was distraught and I was distracted as hell. Hence me leaving the single most important sketchbook I had ever drawn in a NY cab. Along with a full bottle of gin. It had everything in there and I spent the rest of the evening ready to hang myself. I've tried to recapture some of what I did in there, but some things I practiced and worked on were firsts for me, such as a new way of drawing buildings as well as a mock-up of a pivotal scene in a comic I'm working on.
The best I can describe it as is if I were a scientist on the verge of a break-through who loses his vital book of notes and has to fill another pad from memory. My friends who I was visited couldn't understand why I just didn't draw it all again....