"Sorry about that, that I suddenly ran off from you. Couldn't take it anymore. Dove into that bush over there and started...y'know, taking care of myself. I heard you yelling and looking for me, I just couldn't stop once I got going...you should be used to this by now, this isn't the first time it's happened.
Anyway, I feel a lot better now, ready to face the rest of the day. Or at least the next few hours. We can get back to shopping now. If you're embarrassed about the mess, maybe we could get paper towels first?"