200% sure Jim!
Just need to find out which girl he caught, you will have an idea in a month from now if the copulation was a success. This is a classic sperm plug that is often dispersed via the females cloaca the next day or day after, it a appears a little discoloured due to it being in the tank a few hours.
You have waited a long time for this, I sincerely hope things go well for you.