When a book has an ISBN the trade buyers from any store are able to find it listed, and then procure it to stock, if they wish to. With that ISBN your books will be placed on the Barnes and Noble's website, anyway (and many more) and people can buy it from there, and even use Click & Collect to obtain it. (Order on line, pick up in local store.) It's not as if B&N will not know your books exist because they end up on their website simply by adding a Lulu ISBN.
Does it make much difference if hardcopies are not actually stocked on real shelves?
There's also the problem with the base Cost of POD. It's far far higher than with mass-printed books. Add to that what you want to earn, add to that B&N's 50% (and possibly + taxes too.) That can put any bricks & mortar retailers off stocking them. Shelf space costs them money so they want a fast turnaround from it.
A further potential problem is that even if you have a number of books printed for some retail bookshop to stock, they will expect Sale or Return.
I just want to be the best of being a writer
Just Kevin said:
Simple. don't use the grammar checkers at all, and also do not rely on the spell checkers. I have to say that a proficient writer should not need them.