Hm... It's totally okay, to not be able to do it. Nobody can know everything. Doesn't mean you are in a "lower" category compared to your colleagues.

Okay, it's not a global problem (ie. "needs PHD") but just a personal problem (ie. "I have no clue how to solve it"). Trying to get as much stuff done as possible, I've said similar things in the past, though. Not really thought about it before typing. Happens...

Nobody got hurt in the process, right? Let's forgive this little misinterpretation and move on.