Don't carry this too far, the owner of a federally registered trademark can sue the hell out of you. I would not play this wait and see game. The trademark database is easily searched.
I think his point was that you shouldn't redo everything because someone phones you up claiming to have a trademark. Give the response he mentioned then go do your homework. If you're actually infringing, it's prudent to stop before the lawsuit arrives.
Edit: US Registered Trademark search: http://www.uspto.gov/trademarks/index.jsp