Actually, hiding the IM teleporter is deliberate on my part so as to avoid this very tactic or at leat make it difficult. I do plan in the future to enhance shapes, which can be visible, so that they can do a variety of things from provide nrg to perhaps teleport intra-sim or even between private sims, allowing those teleporters to essentially be visible, but I think the IM teleporter should be invisible at least for now to make this kind of swarming attack harder (but not impossible).
There is nothing to prevent very smart bots from using clever ways to figure out where the IM teleporter is. IM teleportation is not random. The IM teleporter drifts from one place to another, potentially leaving a path of disappearing bots. One can imagine a bot probing for the existence of the IM teleporter by watching other bots disappear or even actively launching low-nrg offspring and watching to see if they disappear for some unexplained reason....
I should also point out that multi-bots get teleported all together, so one might imagine a bot that forms multi-bot clusters in it's home sim or one that it has conquered but separates once teleported to a new sim (determined by the ratio or *.totalmyspecies to *.totalbots) so as to arrive in numbers....