The Saracens back was excluded after a deal struck with English clubs meant that only five players from south of the border could be selected for the Guinness Six Nations game in Paris on Friday.
Maitland was the most high profile of the English-based members to drop out of the squad.
“He was really disappointed, as was Jamie Bhatti, who has been on the bench for us the last two weeks,” said Townsend, the Scotland coach.
“There are other players who may have come into consideration like James Lang, Duncan Taylor, Cornell du Preez, other guys who had been in our squad.”
The match in Paris should have been played last month but was postponed due to a coronavirus outbreak in the France squad. It was rearranged for Friday but the new date sits outside the regular Test window, forcing the Scottish Rugby Union to negotiate the release of their English-based squad members.
A deal was finally struck on Saturday night, but for the release of five players only.
Townsend refused to criticise the terms of the agreement and said it was better than looked possible at one stage.
“Look, it’s much more satisfactory than I thought it was going to be on Saturday, when none of our [English-based] players were going to be available and we were putting together a team of home-based players plus Finn Russell.”
Russell was released to play by his French club, Racing 92.