Keep your ears clean and keep your eyes open. You can usually hear the ESTps. They don't really disappear into the crowd. They are the first ones to try new fun-fun things and they are the last ones to chicken out. :wink:
EDIT: ...because ESTps are everywhere. They like new activities, so they are likely to often try new things. There is always a chance of bumping into ESTps in every activity group. They like LARP, they like D&D, they like archery, but they also like travelling, sports, etc. They might not stay with the hobby for long, but if one ESTp leaves, there will be other ESTps to spend some time in the activity group. They are everywhere, you just have to spot them.