Notes:

"Items that fall to the ground in Stardew Valley -- wood and seeds from a felled tree, loot from a slain monster, et cetera -- get sucked into your inventory/body by a powerful magnetic force. Items you intentionally drop also fall into this category, so I often find myself dropping garbage on the ground and then running away from it like a live grenade.

That's probably why your inventory has a trash can, allowing you to permanently delete an item on the spot, but what if I decide I actually really need a moist fistful of tree sap?"

Source