Actually, that instant sell-out is the best market research you could get! It proves real demand instead of just guessing what might sell. Now you know for sure it's worth making more.
Wow, that's a crazy good problem to have! But @finleyl39 and michaelgrant are onto something, it flips from exciting to scary real fast. Are you already set up to make more right now, or is your supply totally wiped out? That kind of instant sell-out can really show you where your weak spots are before you get in too deep.