If that's what they were really looking for, then they're really just testing whether you can figure out what they're really looking for, whether they know it or not. If you want someone to demonstrate their thought process, you give them a tricky problem and just tell them to solve it out loud. If it's a good problem, they're not going to be able to fake having an awesome thought process.

"I'd google it" is exactly the right answer, as far as I'm concerned. Unfortunately, it's never the answer interviewers want to hear. Regardless of whether they've asked good questions, it's invariably one of the most common responses interviewees will make when they don't know the answer. Whether or not the interviewer had a justified expectation that you should know the answer, "I'd google it" immediately gets you downranked by association with people who don't know their shit.