Can I get a weird judgment? (ie, an assessment of how bizarre something is...)

A few days ago I arrived at work to find someone had undertaken a MAJOR makeover at my desk. Now I'm a science graduate student, so messy desks are par for the course, and mine runs in the middle of the pack (not too messy, not ocd tidy). Whoever had cleaned everything had really taken it to the next level, including going through and rearranging all my papers, and also making artistic rearrangements of some of my belongings (moving them from desk drawer to shelf, etc).

This made me feel extremely uncomfortable for several reasons. To begin with, my boyfriend works in the department and everyone knows we are in a relationship (and I know it wasn't him pranking me, we were together the whole night), so I wouldn't think this was a secret admirer. Also, I have lots of data laying about, none of which is 'exciting,' but some of which is interesting and publication worthy. Also, I have been stalked before (not too seriously, and in another country). Nobody stepped up to claim responsibility for this tidying, and when I asked around, nobody has had this happen to them before (so unlikely to be the cleaning/maintenance crew).

So I'm working with someone who decided to secretly rummage through all of my belongings. I feel very weirded out, but am I overreacting? Might this be a harmless gesture?