I've seen this happen and bug reported it. First saw it happen months ago. Someone else is reporting a similar issue in another thread, so its not just me. Given its not been acknowledged, I figure this is the thread to put it in. I've seen this 5 times or so, so its not that common.
See item on ah 2 days left
Place low bid on item, there is no buyout on item
Item appears in my bid window and is there normally over next 24 hours.
All of a sudden item is in my bid window (and on AH) with 3 days left at a higher initial price (i.e. relisted).