That tank has all manner of odd invertibrates in it that can only have come in on plants (there's a lot of new ones in there, all from Oriental). All shrmip are accounted for so I *guess* damselfly larva don't eat shrimp. At least adult ones.
I found two nymphs (on two separate occasions) in my tank. Nearly made me wet myself . The LFS that I buy most of my plants from does receive large orders from Oriental, and I've seen damselflies flying around in the shop. Even found a nymph in a bag with plants right after I brought them home. I guess it's just "one of those things" you have to put up with when you treat yourself to those rare, exotic species of plants from the Far East . I suppose it's a tad better than ending up with a mantis shrimp from buying wild-harvested frags. Sort of.