I go to the kitchen to grab thing B. However, on the way to thing B also lies a thing A that I have to grab.
I can either grab thing A on the way to thing B, or grab it when going back after grabbing thing B.

I grab thing A on the way to thing B (option 1) because I know that it's better to grab the thing the first time I see it before I forget that I need to grab it.
On the way back, I no longer think of option 2.
Now, a question.
Is there a way to determine whether I didn't think of option 2 because I had no need for it or because I forgot about thing A (like I assumed I would)?