The Seagulls boss may have been disappointed with a goalless draw at the npower Championship's bottom club Bristol City but was instead pre-occupied by the injury that forced his striker from the field.
Mackhail-Smith went down sharply when breaking away from Liam Fontaine's challenge just before the interval and immediately signalled for attention.
Poyet said: "It looks bad. Craig could be out for two or three months so his season may be over.
"I don't like the emergency loan system, but I am not so stupid that I won't use it as we are now very short of strikers.
"I'll start looking for a new striker tomorrow. It was meant to be my day off, but now I expect to spend most of it on the phone."
Brighton failed to force a single save from City keeper Tom Heaton and Poyet admitted: "It is not a game I shall be watching again.
"The result is everything. We couldn't pass the ball on the night and didn't play well, but we did the basics right to get a precious point."
