Law is now looking into extending the loan of Rankin, who should return to training in the next week.
"I still think we need something up front. Isaiah Rankin will hopefully be returning to training next week - that will be a big plus. He may have been the difference tonight, he may have been the Mooney for us," Law told MarinersNet.
"His loan is up on the 20th, so if he is anywhere near fit, we need to be extending his loan until the end of the season. Even if he is a week, two weeks away, he will be a vital player for us."
Law also added that he is still looking at additional loan faces from Premiership sides, but is not getting his hopes up ahead of next Thursday's transfer deadline.
"Since I've been here, every day has been frantic on the phone to everybody. We're talking to Premier clubs about young players that are just coming out of their academy and they're even reluctant to let them out. I've made a couple of calls on the way down and maybe there could be something tomorrow - but I'm now getting too excited," he added.