The 500 saw him at the same time:
After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep. 1 Cor 15:6
Jesus had been seen by many. For example a huge crowd witnessed his entry into Jerusalem a week before his resurrection. The 500 may have seen him in Galilee.
As they entered the tomb, they saw a young man dressed in a white robe sitting on the right side, and they were alarmed.
“Don’t be alarmed,” he said. “You are looking for Jesus the Nazarene, who was crucified. He has risen! He is not here. See the place where they laid him. But go, tell his disciples and Peter, ‘He is going ahead of you into Galilee. There you will see him, just as he told you.’ ”
The Apostles may have gathered the 500 in Galilee. In any case the fact that the 500 saw him at the same time means that those who didn't recognize him would have been made aware that it was him.
This is what I would surmise. The evidence is diluted because it is not really 500 witnesses. It some smaller number, who are told it is a resurrected Jesus, by others.
There may be other information. I think some texts say they saw Jesus ascending into the clouds?