IME if you heard the thud you should find something, rain or no rain. Rain will wash away blood but there should be hair where he was when you shot. I have in less then great light hit an animal and when to where I though he was standing only to find he was 15-20 feet further from me then I had thought when I shot. Bad light will play tricks like that. The best bet in that situation is to get the correct line and then search near and far on that line until you find something. Trust me it's there if you hit him.
Now, after waiting out a night of rain it'll be damn tough to locate any sign. Blood will have washed away and tracks will fade and be covered by falling leaves. IMO you should have been on his trail knowing that rain was in the forcast or even if there was a question of rain. I'm sure your hindsight is pretty clear though.
I heard a satisfying hollow chunk as the arrow hit and he ran about 60 yards and looked back at me.
By his reaction I question if he was actually hit. I've shot quite a few deer with a bow and have never had one stop running within sight after they started unless to pile up. I've heard of (but never witnessed) a deer being hit and standing in place but if you startled him enough to run if he were hit I think he'd have gone a lot further. I'd be looking for you arrow in the ground/leaves in the line of the shot.
I may be wrong but IME and opinion I question the hit. I also question how long you looked. did you look down hill, at water sources, or on the most easily traveled path in the direction the deer ran. If I were you I'd still be looking. IMO you took the shot and owe it to the animal.
Ahhh yes, Welcome to the forum.