Cue, I consider myself a stand-up player. I can't say I've always been this way but throughout most of my playing days, I've tried to be. I think anyone who has played me in the past 10 years (at least) can attest to this. I abide by the rules, do my best to protect myself from the rules' pitfalls and allow a bit of grace for my opponents. I expect the same in return. At times, I'll even demand it. There are plenty of scenarios in the rules that allow for reverse calls. Of course, the situation will dictate its importance but I can assure you, when the call is appropriate, I've abided by it.
In this scenario, there is a 99.9% chance I'll inform my opponent he is on two fouls just prior to his return to the table. In the rare instance that I might tell him before, it would be in a scenario where I expect to be at the table briefly and I'll await acknowledgement before proceeding. If this is insufficient notice for him and it becomes a situation where a referee is needed, yes I will call him out on it. I'll argue my case loud and clear and by the end of it, everyone in the poolroom will be aware of what happened. I'll continue play but be rest assured, he might want to call a referee over for any other situation where a reverse call can be made.