It's been about a week with no signs from Larry and then today he came back! He let us pet him but wouldn't eat any food we tried to give him which makes me think someone else is taking care of him.
Some strays have a fairly large "range" and will often disappear for a few weeks, or even a few months at a time. One stray I used to take care of would disappear all summer and come back in the winter. ( He was probably still around sometimes but not operating during normal human hours, but we've also seen him wandering across town on several occasions.)
Either way it sounds like you're really gaining his trust!