Dedicated Server "STEAM: Failed to respond IP:[MyPublicIP]" Suggestions?

So then it’s not surprising that you receive matches from someone else also using this test ID.
I recommend actually signing up for the Steam development, and using that ID for your game, and chances are, you’ll get the matches you expect.

Another alternative is to set some particular property on the match listing that nobody else is using (like a specially named game mode or whatever) and use that to filter the listings/search. That may also work in the short term.