The cat was found in a small cavity wedged in behind three, large rectangular boxes, he said.
"I've got no idea where she came from and I've been racking my brains how she got in there. Cats love the vans and she's obviously gone in to have a sleep.
"We're often on people's properties with the doors wide open and it's not unusual to get back to the van and find a cat asleep on the seat," Mr Bell said.
"I'm just glad she's all right. I love cats. I've got two myself at home."
The unenviable job of extricating the mobile moggy went to SPCA inspector Julie Richardson.
"I've never had to get a cat out of a van in a situation like this before. She was hissing a wee bit and I had to shuffle into the hole to get to her. But, she didn't seem to be dehydrated. She was pretty scared, but in good condition."
SPCA officers checked, unsuccessfully, to see if the cat was chipped and it hoped her owner might recognise her.
"She's a lovely cat and it would be really nice to find who she belongs to," Mr Bell said.