(Disclaimer: I recognize that many people overuse the term OCD to reference organization tendencies rather than legitimate obsessive thoughts and/or compulsions. The person in this situation self described as OCD so I am taking them at their word.)
I was in a coffee shop drinking a tea and chatting with a friend. This coffee shop had a long center table and several small side tables. An employee mentioned it was kind of driving her nuts that people were swapping chairs from the center table to side tables since, it both made the chairs at the long table not match and that the center table and the side tables were different heights so the chairs were different heights so people should notice the chair felt weird and really this just made her all OCD and while she certainly wasn't going to wrest chairs away from the butts of patrons she didn't know why other people weren't bugged. (This, I should mention was said entirely in a friendly if curious tone, when you legitimately wonder how people suffer the bother of the unmatching chairs.) I and my friend immediately checked our chairs. (Mine was right, me friend's was wrong.) And this led to a discussion of how there were tumblr and pinterest sites about organization, and I mentioned that while my apartment was often a mess, I was one of those people who went into the drug store and rearranged the lipsticks so they were back in the correct slots.
Well, my friend and I got up to go and were at the corner outside when we heard behind us, "Wait! Wait!" and the lovely coffee shop staffer jogged out hand handed me my bag of goodies from the holiday market, including a
yummy hat kit I had purchased at the holiday market. I thanked her and then realized that while she was clearly a lovely and attentive employees, it was probably her desire to fix our chairs that had her realizing I had left something behind so quickly while I probably would have remembered when I got home. So really, OCD saved my knitting.