GB + Lance vs Warning

So let's say during my battle phase, I attack with a Gladiator Beast, he chains Dimensional Prison in response to the attack, which I then chain Forbidden Lance. At the end of the battle phase, I decide to tag out, once returned to the deck, can my opponent chain Solemn Warning? Or is the Forbidden Lance "unaffacted by Spells or Traps" effect still in place?

Thanks!

The GB returns to deck as a cost.

Since it is no longer on the field, forbidden lance does not affect it. If warning is activated, the GB "dies" in the deck and its effect is negated.

Select 1 face-up monster on the field. Until the End Phase, it loses 800 ATK, but is unaffected by the effects of other Spell/Trap Cards.

No protection unless face-up ba.. I think that's how it works..?