If the seller does find the receipt, the boutique may still be able to obtain the screw, I suppose?
Maybe you should call them and see if they can, before you buy it?
The problem with having a cobbler do it, is they, almost certainly, won't have a matching screw. I've seen Chloes on eBay with replacement studs, where the cobbler has, apparently, told the seller he can provide a similar one and they are totally different!
If it's a real bargain and you don't mind that (bearing in mind it will affect future resale value), then go for it, but if it's quite pricey and you can't get a matching screw/lock I think I'd probably pass, personally.
