Oh, I would
love it if
Megalodon still existed

!
Although, I guess we'd need to look for smaller animals in relatively isolated locations (for example, deep underwater or in dense jungle). I guess more recently-extinct animals would be more likely to resurface too - although, the re-discovery of the coelacanth demonstrates that that's certainly no requirement

!
I wonder about the pig-footed bandicoot, for example. It hasn't been seen alive since the 1950s - but, it had a range which covered vast swathes of inland Australia (which is
very sparsely-populated). Maybe there are still a few of them hiding somewhere?