When your inventory is full and you get a item+bonus item, the item in your 1st slot will be deleted and you will only get the bonus item.
Another thing, if you get a bonus item thats an active item, it wont go on your active slot hotbar and you wont be able to activate it. (had this situation only once so not 100% sure about the interaction).
Another thing, if you get a bonus item thats an active item, it wont go on your active slot hotbar and you wont be able to activate it. (had this situation only once so not 100% sure about the interaction).