If it somehow happens to be either polish or wax, for household products you may have lying around, you could try a 50/50 dilution of IPA, but I'm not sure it's going to do anything here. YMMV, as some dried residues, even very fresh polish residues (such as Meguiar's most popular polishes) may require dedicated paint cleaners, something beyond an IPA wipedown.
If you trust their detailing dept (unlike myself) I guess that is the easiest route available to you. If your trust starts wavering, you could ask them what that residue is (I won't be terribly surprised if they can't even answer that for you), and once you have that information, post your question at a dedicated detailing forum that the pros frequent. You see, some polishes and/or waxes are much more difficult to remove than others.
If that is wax residue there, that is WAY too much. Many waxes need the very thinnest of layering, with overlapping machine strokes to guarantee coverage. For example a common technique with a liquid sealant is to get a very small bottle, say 1oz, fill it about halfway, and then use half of what's in there, for only about 1/3 oz or so for the entire car. You can add more layers after the first cure and wipe, etc. That pic would be mega gooped on right there. If it's a polish, well it's hard to imagine missing that before a wax. Maybe some sort of AIO? Maybe better ask the pros, there are a few very top ones that frequent the detailing dept here.
Yes. I scrubbed it a little more than lightly with a microfiber towel that was dampened with quick detailer. It would not even come off with some light fingernail action.