‘And it came about that when Jesus had finished commanding his twelve disciples, he departed from there to teach and preach in their cities.”
Then once Jesus had given His instructions to His twelve Apostles He left them in order to preach and teach in their cities.
Matthew give no indication either that the Apostles went out, nor what happened to them on their missions, nor that they returned. That is all assumed on the basis of the instructions given for the purpose. His concern was not with the Apostles but with Jesus. And while Mark and Luke give a little more, they are also very reticent. None are interested in the detail. The assumption should therefore be that much of what His words said did happen, but was so much like what later happened to the Apostles that it was not see as worth mentioning.