there's usually a buy and wait option as well
seems to me like the shop didn't do anything wrong, though - you were just too slow
if you see an email saying a module you want is back in stock then buy it immediately
do not wait do not pass go do not collect 200 of whatever major currency you use - just buy it
almost, if not all, production runs of eurorack modules are 'short runs' mostly in the hundreds or less, these then have to get distributed between retailers - so each retailer might get 10 or 20 modules - so selling out very quickly is not uncommon especially with corona added demand - it's not like white goods where they get delivered by the truckload
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities