The shop is full of....
Once they are sellable size, dime body size or better they are as hardy as most any other commonly found tropical fish. This is provided they are properly bred, ask where they get their angels from. If they are shipped from overseas forget it, they probably will die. Farmed angels aren't much better.
Locally bred angels around here survive 12+ hours bagged at an auction, then get transported back to buyers tanks. Every bag I sell has my name & phone number on it, the only calls I get are folks looking for more fish. I go out of state to auctions, and also buy potential breeders at out of state auctions, these fish go through the same long day as the fish I'm selling. I rarely lose any of the angels I buy.
I've also gotten angels shipped in, 24 hours in transit, with no problems.
I make it a habit of giving 10% over the shop's order, no charge. This is just in case a few don't make it in customer's tanks. I also tell them from the beginning, and reiterate every few times I'm there, that I need to know how the fish do in their tanks, as well as in the customer's tanks, whether it is good or bad. I also offer the shops a replacement guarantee, as long as their water tests out good. I have yet to have a shop call for replacements.
If the shop you got the angels from doesn't operate this way they are the sort of shop breeders like me won't sell to, I'm pretty selective that way.