Just my speculation...perhaps he hung the sheet to identify which room he was in if he was expecting a delivery of something he needed to acquire that could not be purchased over any counter in any store. Perhaps he waited there as long as he could or was told to go wait where he was later found. I can think of no other logical reason to hang a sheet when there are perfectly good drapes that can be closed to block an outsiders view.Photos of the hotel are available and yes there were window treatments. At some point NR hung a sheet over the window, reportedly. I offer no interpretations.
moo