It wasn't a blanket IMO. JT only saw the child's legs and so could not describe any other part of the body to the artist. However to have left an empty space in that part of the sketch would have made it look very odd. Therefore the artist filled that gap with an indiscriminate pink blob to give anatomical realism to the sketch.
AIMHO
That is my point. If it was a father carrying his child back from the creche the long way round, he would have covered her legs with a blanket. The person claiming to be crecheman admits to having a blanket so I'm sure he would have used it, therefore Jane would have been unable to see the legs and the pyjamas.
Therefore I contend that Tanner person and crecheman are two separate people, and would require 2 different sightings.
What does Horrocks say about Crecheman"
"This timing also does not fit in with the sighting by Jane Tanner at 9.15pm. However, we are told that the person who Jane Tanner saw has come forward and been eliminated. I do not know how the police can be sure after so many years, that the person they spoke to is one and the same who was seen by Jane Tanner. Did she meet him, were the clothes identical to those she described? I obviously do not know, but regardless I still think that this is still the most likely route taken by the kidnapper."
From that he sounds sceptical that Tanner person and crecheman are the same person.