Maybe it was a tomato hornworm I encountered then. It was the exact shade of green as the tomato stems and branches, it looked fat and short like a grub, and it took a fight to pull it off because its grip was so strong.
Sounds like it.
They are big suckers and the very first time I encountered one, I had no idea something that disgusting existed. I must have set some kind of record for backward standing broad jump.