I would guess anywhere between 1 and 10 years. But that's entirely a guess.
A lot of factors go into how long it takes for all of the flesh to decompose and the last strand of hair to decompose or be dispersed. All they need is a single strand to determine hair color, and it may have been found within the clothing (i.e., protected from the elements).
On a different Indiana case involving skeletal remains, they estimated that the remains were there for about 2-5 years, and there was still cartilage on the bones, but it was unclear whether the body was initially buried. (it was found in a farm field and the remains had been spread around by tilling equipment)
The comment that there was no flesh on the bones came from the man who discovered the remains, and he probably only saw the portions that were exposed above ground. I doubt that he was able to examine the remains enough to determine whether the buried portions still had flesh on the bones.