If it’s possible, ask a neighbor to keep an eye on the cat. If you say that he goes outside then it’s possible someone else might be feeding him as well.
Cats are usually very resilient. We were feeding a cat for more than two years, but then due to an issue with the other residents we had to stop feeding it. He naturally adapted. We didn’t see any decline in his health which meant he was getting food. Also, from time to time he would see us and come over but not ask for food.
Also, as my vet says, cats have an amazing talent for finding people who can feed them.