eli rabett observed in a comment to a prior post about reading the literature that
Graduate training is designed to pass lore from advisers to students. You learn much about things that didn't work and therefore were never published [hey Prof. I have a great idea!...Well actually son, we did that back in 06 and wasted two years on it], whose papers to trust, and which to be suspicious of [Hey Prof. here's a great new paper!... Son, don't trust that clown.] In short the kind of local knowledge that allows one to cut through the published literature thicket.
This is true but one can't take it too far. Lab lore can be another term for superstitious behavior. It is possible that "the way it works" is really just one of many ways to get something to work...and perhaps not even the best, most efficient or most clearly interpretable way.
There is another realization that comes along with time and reinforces the suggestion to ask senior professors things but not to actually take their angle on the matter.
As you move into early and middle independent career you may find yourself asking the senior Professors why X finding was never followed up on when you run across a fascinating bit of data in the old literature. Or perhaps you will ask whether Y was ever observed after having a "gee that's not supposed to happen" moment in your own studies. Maybe you will need to inquire why the field does it like Z instead of the way that makes most sense to you.
This can turn into a research program or two if you are paying attention. Sure, if you ignore collective wisdom that doesn't necessarily appear in the published literature, you run the risk of wasting much time re-inventing the wheel. I've done that too. And I will admit that there are several of the most curious leads that I have run across that I simply have not managed to turn into a research program yet.
However. There are ideas such as these that have turned into at least a R01 level funded project and resulting papers.
So don't necessarily take the good Professor's word that "I think Professor Schmoe did that back in '68 and didn't get anything" as being the end of your inquiry.