Concept

Yes, but you go into a Walmart or BabiesRus, you know they are going to have a restroom

Baring some type of renovation or special circumstance you bring up a good point. This could be circumstantial and the op works in a large chain like that. I'd concede your point except for one detail- "no we shit outside like bears." That is not circumstantial. It implies that the alternative to not having a bathroom would mean one is not human. Not that the idea is provincial or low class (ie: "poo outside like hobos" or "use the gas station like junkies") but that it is an alien concept to the human race. To your example not: "no, we are the only walmart with no bathrrom" or: "Sorry, they built a store the size of a stadium but forgot bathrooms" etc. So while I agree you are right, it's still imho bad sarcasm as it implies anyone asking is stupid including those in special circumstances. To be well done there should be no reasonable retort, or the sarcastic one looks stupid not the recipient.

Also not all bathrooms are accessible to customers. And the question also implies "can you point me towards the bathroom".

Yes. In a strict sense it's like defining "may I" vs "can I." Arguably one may be better than the other (although it's both simpler and more complex than most make the issue.) So speaking to a human and native language speaker they should likely realize your intent. For instance you could say similar about asking "may I use the bathroom" that you may not have a bathroom. In simple programming that's likely an error. The answer is neither yes nor no because the bathroom doesn't exist. Logically one would need to confirm it exists before getting permission. In reality asking permission should confirm it exists as understood through context.

*Customer coming up to a group of employees leaving a dark store at 11PM* "Are you still open? I just need ONE thing"

It's a way of checking that it's still okay to enter, to see if the person can take another customer. I think it's nice of them to ask rather than waltzing into the restaurant ten minutes to closing time.

It's not okay when everyone is leaving and the store is dark. That stops being nice and starts being asinine. Also, I have had people try to stop me as I was getting into my car after my shift to help them. No. If someone is obviously off the clock, do not approach them.

Some restaurants close the store to new customers early, but continue to provide service.