The presence of "for sale" signage on an REO property is weakly correlated to its availability. Intuitively, your reaction to seeing a "for sale" sign is to think that the property it sits in front of is for sale. Often that is the case. Often it means only that the listing agent has a pending sale in escrow, or that they have a "pre-listing" agreement with the REO bank. - A pre-listing agreement means that the agent is working to get the property ready to put on to the market. The sign goes up. However, the listing agent still has to work through issues such as getting debris hauled out of the property, waiting for the bank to obtain transferrable title, mitigating hazardous safety issues such as broken glass, and gas leaks.
Most Realtors don't put up their own signs. We contract with a specialty sign company to do that for us. Usually the sign order goes out the day the listing is put in the computer, the sign company usually gets the sign up in a day or two. The sign company may have had a delay in putting the sign up quickly due to the weather.
Very few Realtors make the extra effort to put a pending sale rider sign on their signs, and just leave the "for sale" sign up all through the escrow. I am an exception. I consistently put a "pending sale" sign* after a listing of mine sells. But, that is just the way I am. Most agents don't bother to do that.
*The main exception to that is if the seller demands that the pending rider NOT go on. That demand is rare, but sometimes happens.