If they know where to look. Remember the smaller the object you can see means the smaller the area you can look. And even at that resolution, it might still be difficult to say that x spot really is the lander.

One reason why scientists can point to Viking, Pathfinder, Spirit, and Opportunity on orbiter photos is that the landers imaged their surroundings. Then they try to recognize mountains and other
features the landers on orbital images and then calculate where the lander must actually be.