That is interesting. I have heard of that once or twice before but I never experienced it myself.Hey Scott, What do you think...Years ago I cleaned a carpet in a master bed room and placed an airmover in the hall at the entrance to the bed room ( the carpet was white )...before I left right in front of the air mover it was brown, I recleaned it it came out ( I think I sprayed brown out on it first )...but it got me thinking that using a airmover made that happen, and if I had not...It would have dried au naturale and been fine...In other words the forced air made that happen?
Basically, wicking happens during drying. If the drying happens faster, the wicking also happens faster. But wicking would also stop sooner since the carpet is dry sooner.
For soil to wick to the surface, it must be there in the first place and it must have been loosened from the fiber by the cleaning solution and whatever agitation was used. More thorough prevacuuming and slower or additional wet vacuum passes should get more of that soil out of the carpet rather than leaving it so that it can wick.
Whatever level of wicking happens would be more noticed on white.
The main reason for using an air mover is so that the carpet is as dry as possible before you leave. Then you know if wicking is going to be a problem. You can deal with it while you are there rather than having a surprise that brings you back later.