Just a suggestion - whenever one of mine does anything 'different' - softer stool than normal, hairball, whatever, I now mark it in a calendar and try to write down anything that happened different on that day or the day before 9different food, more food, more treats, I didn't brush them as much, whatever. If it keeps up on a regular basis, then I have something I can show the vet to see if there's any sort of pattern.
With my guy, loose stools has been associated with too many greenies (my fault, I know) - but I finally figured it out by looking at my little calendar. I think Dante just has a more delicate tummy, and that's what happens, although he adores Greenies and will attack the bag if I leave it out for a second.
I don't think vets get too upset if it's just an occasional thing, and resolves quickly, but maybe tracking it will help you determine if it's happening more, or less, than you think, and why? Anyway, hope all goes well for you.