Gavin, if there was a gap between carpet & skirting it wasn't on the grippers properly, it needs to be tucked right down between gripper and skirting. As Mike said it could have been cut a bit shy and they over-stretched it when fitting.
OR...
A Wilton will not be flexible across the width of the carpet, an axminster will be flexible in both directions. Wiltons therefore don't tuck in behind the gripper very easily down the sides, so easy to come away
Could be a sign of previous shrinking... sorry, "returning to proper size"

Don't worry mate sh*t happens, you just have to handle it well with the customer and make sure the outcome is positive for them.
I'm cleaning for a customer tomorrow whose dining room chair I damaged once! I took it away and got it fixed, brought it back the next day and they've remained a good regular customer ever since.
And I have to agree, cancel the fitter for tomorrow, get him back on Friday or Monday