I assume that "donation" also doesn't include graduates giving things to returning students. No way to even track that.

This amount doesn't really surprise me. This has been happening ever since students were in dorms. Even in my little liberal arts school, people would dumpster dive for stuff in the dorms where the rich kids lived. The dedicated divers would even go around after Thanksgiving break and the end of fall semester, when the kids who were too into partying left (or were kicked out) and just left stuff behind that the RA threw out.