Mr Theijssen said the reward was money they had saved for a holiday.
Joanne Austin, owner of Siamese cat breeders Brenner Cats, said that despite Siamese kittens selling for about $600, Jet's age meant he probably would not have been taken for his financial value.
Ms Austin described Siamese cats as having "dog-like personalities".
"Some can be taught to fetch, they're a lot more active than a lot of other cats," she said.