On the road they meet Jesus but don't recognize Him and they explain their disappointment with the crucifixion of Jesus on Good Friday. But then Jesus says to them "You foolish men! So slow to belief the full message of the prophets!", and He explains the scriptures to them while they walk their way.
It is easy to remain in unbelief, not to belief what is said about Jesus but to maintain only to belief when I can see for myself. We don't know if Thomas actually ever put his finger into the side of Jesus. Possible the shear encounter with the Risen Christ might have been enough to recognize Him, and to recognize him not only in his humanity, as the Jesus whom they knew, but to proclaim "My Lord and my God!"