I am wondering if the following is grammatical and idiomatic.
I really love the restaurant but haven't gone in a while.
Is the word 'gone' used correctly here?
Both are acceptable, in my experience as an American English speaker. However, this probably varies with regional dialect.
When talking about the act of going to restaurants in general, I generally use "gone," as in "I haven't gone to a restaurant in a while."
When talking about a specific restaurant, I generally use "been," as in "I haven't been to McDougal's in a while," or "I like Larby's, but I haven't been in some time."
However, neither one is particularly strict; it makes perfect sense to say "I haven't been to a restaurant in a while" as well as "I haven't gone to Ruddy Tubsday's in some time."