A bid can't be retracted or cancelled in the 24 hours before the end of the auction.  So someone could make a decent bid (obviously the last bid was higher than yours, but it will only register as a high bid once you have bid) and then inform the seller that they want to, but cannot, retract the bid.  The seller would merely relist, though now with the information that the item - had it sold - would not have made the sum the seller had hoped for. 

Or simply put on buy it now while waiting for the next 80% off offer to come along again.

Or the buyer might have asked the seller to cancel for a change of mind.  Always better to cancel than to have a return.

Or she could have just had someone bid it up.

You will never know, because the seller is not obliged to explain anything to anyone.

But another one will come along - and might even be cheaper!