Its possible because alot of people do come forward after the guy is caught doing something heinous and saying "I always knew there was something weird about that guy..."
But all the reports have a "witness saw her walking toward Escondido High with a tall, slender, dark-complexioned young male" who has never been located or identified. Which is sure a long way from the Gardner description of a "white male in his late 30’s to early 40’s 5’11” tall with a stocky build with a large belly dark brown hair that was clean cut with medium spikes on top". So what happened between skinny dark young male and stocky white middle-aged man?
It just seems strange to me and makes me think that he had help.
A lot of times eye-witness accounts aren't reliable.
For all I know the witness who thought she saw Amber with some boy was mistaken, and whoever this witness saw wasn't even Amber.
It's not Gardner's MO to have help so I very much doubt he had any help in Amber's case.