It turns out that my co-worker had his seat stolen/swapped as well. In the end, he had my post and seat, though I didn't have his. He still was willing to swap, as the seat was better. Mine had a rip. So someone went to the trouble of swapping at least 3 or 4 bike seats and posts. Maybe they thought it was a funny April Fool's Day gag, but it was a total d-bag move (and in the end, my co-worker still lost his seat and got a worse one in exchange). Don't touch stuff that doesn't belong to you. It isn't really that hard to follow.
When I got home (I did bike home, but had to go more slowly than usual, since I hadn't brought a change of clothes, since I didn't expect to be able to resolve the bike issue until Wed.), I finally changed the seat for one I had bought last year. That felt like a decent accomplishment, since it isn't something that I had ever done before. I also did a bit more weeding, so the yard doesn't look great, but at least it isn't full of weeds. That was pretty much all I accomplished, though I did run through the script for Final Exam one more time, as the first full rehearsal is today! Hope it goes well.