I don't think anything is impossible, you just made an insane leap. Of course he knows Ros wasn't his girl. Tyrion having a whore at court isn't exactly the best kept secret. Cersei, Varys, and Tywin all know for sure, even if they don't know which whore. LF asks "how'd she get that idea" that Ros was his whore....shyt, she probably got that idea from LF who knew she was in Varys' ear.
If Pod didn't lay that pipe, then why did Ros say the girls can't stop talking about it?
Pod could be snitching, you just made a gross leap in logic to confirm it.