Wolves boss Julen Lopetegui was left frustrated after Sunday's defeat at Newcastle.
Substitute Miguel Almiron scored the winner with 12 minutes left as the Magpies ended a run of three straight defeats in all competitions to leapfrog Liverpool into fifth on goal difference and move within four points of fourth-placed Tottenham, who have played two games more.
Hwang Hee-chan, another substitute, had levelled for Wolves seconds after coming on to cancel out Alexander Isak's towering first-half header.
However, Wolves believe they should've had a penalty for a foul on Raul Jimenez as Lopetegui said: "In the first half they worked through us.
"For me, we should have had a penalty. We are very unlucky with the referee. We were unlucky against Liverpool and then again today.
"In the second half we improved a lot. We changed a lot of things and were able to get at them.
"It was a pity that we had no changes left to make after they scored. We lost against a very good team."