encounter??

one time me and my friend were at this party, and there was an old house down the road so we decided to go hang out in there (i never believed in paranormal, hauntings, etc at the time) me and my friend were just messing around in the lounge room, and on the side of the lounge room there was like a huge glass window (there was a room on the other side, it was just like a separator) and while we weren't really focusing on the window, the movement was definitely big enough to get our attention, it was like a big, almost human shape, that just walked past the window (for about 2 seconds) we both got up and ran into the room where the movement came from, assuming it was someone from the party, and no-one was there, we looked around the room and no one was there, it was basically impossible to get out of that room without us seeing, as we ran straight to the exit and heard notihng after, about a minute after seeing the shadow, we ran out of the house and back to the party, we looked up the street and no one was walking back to the party either. (it was abt a 10 min walk, so we would of seen them if it was someone from the party) i haven't really talked to this friend since then, it was ages ago, but we never saw it again. do you think it could be a ghost? or are we looking into it too much hahaha?