What can and does happen is a neophyte buyer and his realtor may make an offer on a bank owned that clearly has work that will not allow it go FHA so they can't get financing because banks will rarely lift a finger or pay any costs to make repairs... it comes back to "active"...
A buyer gets a contract and ends up not being able to qualify because they didn't correctly factor in all of the monthly costs, i.e. HOA/Condo fees, property taxes, flood insurance, hazard insurance etc... Comes back on the market..
Another scenario is the unscrupulous law firm hired by the lender to foreclose allowed fraudulent paperwork by "robosigners" so they are not able to get title insurance to complete the sale to the next buyer so it has to be "taken off the market" while they "re foreclose".
If you want to find the best bargain, make sure you make your offer on a bank owned the first day it comes out on the market and if it's already a significant bargain at full list price, don't try to nickle and dime or make an offer much below asking or you'll miss out..
Hope this helps.
So it could be the house going on and off the market.
The other factor, in our area at least, is the "days on market". Many homeowners, once their listing has become 'stale' will withdraw and relist their home in order to reset the days on market clock so the listing looks fresh. It doesn't really fool anyone, but it makes the homeowner feel better.