If it has just been "deleted" then yes as the delete functionality does not wipe data it simply removes the index record of where the data could be found. If the data was deleted a while ago, new data may have overwritten it anyway, you just don't know.
It all really depends on against what technical skill level you are dealing with, as that's the primary factor in any "can X be Y" question.
Re keyloggers, hardware ones for laptops are a pain compared to software ones. Commercial (hardware) ones about 150 squid a pop less vat and software ones, commercial again should be spyware free and prices vary a lot as they tend to vary on functionality, ease of use etc.
First question I would ask, is what you are looking at using the keylogger for ? (And no, I don't just mean logging keys )