I would be on my third trip to Lowes or Home Depot by now
I can relate . . .
usually one store or the other will have what I need to complete a project. Checking inventory on-line
usually lets me know which store I should go to, but on-line checks are not much more believable than anything else on the internet.
When I lived up in Minnesota and had a project, I knew I'd have to go to
both Menards and Knox no matter what - each store would have 95%of what I needed, and if I was lucky, the 95% one store had would include the 5% the other store didn't have. (No local Home Depot or Lowe's back then.)
I normally have what I need for minor electrical work, but as for minor plumbing . . . I always seem to have two sizes on hand when it comes to something simple like a gasket or O-ring: too big and too small.