Personally, I'd be more worried about explaining having a second phone than the possibility of a possibly suspicious incoming call. Call history can be deleted and we all get telemarketing spam.
Remember in Breaking Bad when Walter got caught with the second phone? I do.
Generally your okay. But that could change very quickly, ie. such as the situation with the TOE bust and capturing client information. Better just to spend 100 bucks and get a burner phone from Seven Eleven and pay in cash. Pretty cheap insurance policy that you might have wish you had done it.
Also their are sites like www.exposingjohns.com that try to exploit peoples numbers. That could kill your professional reputation. Not worth the risk if you ask me when you could just get a burner phone.
The sex trade isn't yet a LE focus that would justify the expense and effort of winkling out random johns and making cases using the phone numbers at some agency. But it may not always be so. The real issue for today is our habit of leaving our phones—burner or not—and their contents where people we 'trust' can pry into them.
While you ponder that, look into all the apps and features that block and/or sort and process incoming according to number. If you've got the discipline to keep your calls list pruned, block 'touchy' numbers except when you're expecting their calls, and keep those on vibrate only, you'll likely be able to keep your phone(s) safe.