What does he mean by "crushed"? Does he believe it's been in a major accident and reconstructed or was it a minor collision that required something simple like a bumper replacement?
The auto history sites can only report what was reported to the official records, insurance company, etc.
A previous owner could have done something insignificant such as bumping a post or another car in a parking lot and they paid out of their pocket to have the minor damage repaired rather than filing an insurance claim. This would not be on any records available to Carfax, Autocheck, etc.
Also, the car could've been involved in a major accident that caused severe body damage and maybe even frame damage but none of it was reported through insurance or an accident report or whatever due to how it all was handled or even simple clerical error.
By "no visible damages", do you mean the body lines and paint all line up and look good or do you mean there's no signs of repair work underneath (bolts that appear to have been wrenched on, marks on the frame from being pulled, etc.) ?