Many of the auto body shops rely on Allstate, Geico and State Farm business. They tend not to make too many waves on any one repair job, for fear that when they need a damage appriasal adjustment for a customer in mid-repair it may come back to bite them. That's the reality. If the shop has flip-flopped you do run the risk that they caved as they didn't want to make waves w/ the Allstate field adjuster that works their territory.

If you do want to pursue it, you'd need two apprasals that either meet the dollar amount threshold to total it or that indicate the car cannot be safely repaired. Car repair shops are in the business of fixing, so you'll be hard pressed to come by the later even if it's a bag of parts. Getting the former isn't practical as you'd have to have the car towed to two different shops. I suggest you look into an independent adjuster. They'll visit the current shop and since they have no particular stake in making nice with the Allstate adjuster are in a better position to call it like it is. Even if the answer is the same, that will give you some peace of mind.