If the bike shop faced the shell there should be some residual evidence. If there was paint all around the BB face, then that should no longer be there. Evidence of a cleanly cut face, there shouldn't be any gaps with the bottom bracket pieces. For that mater the newer BBs don't always contact the outside face of the BB so flatening that part would not be sturcturally important. One chases the threads to insert the supports of the facer, at least with mine, so you can leave that step out and it leaves protective paint on the BB itself when it is steel. I just don't really see that BB shell fracture as being the fault of frame prep anyway. I could see a loose BB doing that. Some of the ones I use have cartridges in them which makes it at least theoretically possible for the nuts to get out of wack without the cranks feeling all that loose, and that could overload the right side of the shell. Any sign of it being loose?

You say you recently noticed this failure. While you may be owed a new frame, I am not convinced there is any terrible lack of safety in the BB as it is. As long as it has sufficent bearing to hold the cranks firmly in place. If you just noticed the crack rather than feeling something, it may be something that you could get along with for a while.