OP here,

Didn't think I would come back to a 3 page thread! I appreciate all the input. I really do have to wonder if it was a leaky valve stem. I made sure to check the stem area multiple times when I did my water testing. In any case, recent circumstances which would require a long story lead me to think it not entirely unplausible that the 'suspect' would do this. He seems to be an immature and jealous type, even though by all appearances he finally succeeded in woo'ing this certain person - who I've long since stopped talking to beyond exchanging smiles and hellos.

I work at a fairly small company and we don't have a security department to report to. In the past 6 months we had security cameras installed looking over the parking lot, but I don't think they can see the bike rack [it's slightly around a corner]. The two highest supervisors would be the ones to review the footage, but as they have a ton of other 'real' duties [chaotic textbook distribution warehouse], I doubt they will do it. In any case, I sent them a brief email about the incident and requested that they look at the camera footage. It would be easy to spot someone at least walking towards the bike rack [if it's not in view] and then walking back shortly thereafter.

It's not totally out of the question to bring my bike inside the warehouse and keep it near my work area, but I will eventually be hassled about it. We'll see. As much as I want to just straight up ask the guy if he did it, I think that would make the situation between me and him worse no matter if he did or not, and moreover, I think it's pretty dumb that he has some grudge against me anyways. I think I will be extra nice to him instead.