So your an engineering intern and a factory worker complained? It may just be a case of someone feeling like it's unfair and has to do with privelage, maybe the worker was assigned closet cleaning duty, maybe someone jumped his case a year ago for storing something in there. If you really want to know, ask politely. If you're really worried about this bike, get a cheap used one and ride it, or get a couple of locks and lock it up, or ask to store it in your work space, or ask if there is anywhere in the factory where it could be stored..... floor managers and workers often know where the knooks and crannies are.