Hi!
We didn't see a or hear a lot of Littlefoot's mother in the sequels (only in LBT5, 9, and 10) but I guess we can take it for granted that Littlefoot did not sort of forget about her. I wonder if they are still in sort of a contact the way they were in the original movie.
I thought about a land before time story in which Littlefoot is forced to come accross the very spot where his mother died. A land before time fan and poster in the network54 forum considers writing a story in which Littlefoot intentionally visits his mother's resting place.
As for Littlefoot visiting or being confronted with his mother's resting place, it is a delicate topic. One ought not to forget that it would be located far from the Great Valley in a wasteland that provides little food, but many dangers. In fact if Littlefoot went there, he would put his own life at a very high risk. With Littlefoot apparently having a kind of spiritual contact to his mother (Things you see with your heart only) I think there needs to be a VERY good reason for him to go there.
Perhaps I'm too much of a realist, but the direct use for Littlefoot's mother (who told him to go on in the original movie) would be little.
What would Littlefoot find at the place where his mother died?
The most realistic, but sort of uncomfortable variant is bones.
Yet one almost romantic idea would be to show the death of Littlefoot's mother as a process for the renewal of life. Dinosaurs and other creatures may have been saved by scavenging her. Her bones may provide shelter for small creatures protecting them from the hostile land around. Her body (ugly as this may sound) may have provided the fertilizer to let a little green patch grow amidst the decaying wasteland. It could be quite philosophical a story (while I strongly advocate avoiding obvious religious topics in LBT).
But like I said, I think Littlefoot really needs a VERY good reason to take the risk of the journey in the first place. There are no hints that would suggest that he needs something physical like her resting place to feel his mother's presence.