The first time this happened to me it scared me a lot, even though i was aware that it would go back, i came straight back home went on the forum and everyone said dont panic, i had explained to the customer that this was a possibilty so when it did ripple slightly she was not overly concerned in fact i think it showed to her that i knew what i was doing as i had predicted it (thanks to the forum) but i still worried i would get that dreaded call back, it never came.
I remember one guy on here at the time said look out for sculptured carpets they are prone to it and recently had one so again explained to customer during the survey that it may ripple also explaining why and again it did, but no call back.
I think you should have been a little bit more assertive and confident in you response to her and said "it will" go back and not "probably" when it dries completely, if you sounded unsure she will have lost some confidence in you.