Chances are the yeast will out compete anything that may have got in. As long as you had good sanitization practices prior to that you will likely survive, in my opinion. I've done worse and been fine.
The thing to remember is, even with a dry airlock is that the bad stuff are not ninja acrobats....whether it is a 3 piece or an s type, they would have to get through the cap at the top, then either negotiate a series of twist and turns through an S shaped "track" OR have to dive down, then climb up the center post under the plastic bubbler, then lift said bubbler up enough to the make it into the center post and dive into your fermenter....and STILL have to negotiate the rising co2 current pushing out of the fermenter itself....Think about it...Even without water in there, do you think a piece of dust can make this journey?
Needless to say a piece of dust ain't gonna make it. And not much else either. Relax
I just did the same thing, I think the starsan I put in there was all foam and I didn't realize it. No worries, nothing can get in there anyways except an extremely crafty fruit fly... but they can't get through the cap anyways.