Playing on the RLCraft modpack, Placed backpack down to store loot in it and started exploring, Returned to backpack to pick up and leave and the backpack was blown up by a creeper before being able to pick it up in a panic I tried crouching to pick up the items but I was unable to pick them up via crouching even upon right clicking them they would not enter my inventory, during the course of this action another creeper blew me up. Upon returning within a minuet the items from inside the backpack were gone however my items that I had in my inventory did not. Is this intended?

Was your inventory (mostly) full at that time? Both the backpack exploding and items getting destroyed by a second creeper explosion are intentional, the latter being a Vanilla mechanic. However, if you were indeed completely unable to pick up the items dropped from an exploded backpack, that is a bug we'll have to investigate.

I opened my inventory mid panic and saw that I only had 1 and a half rows of inventory at the time however I didn't get a chance to try picking them up again after confirming that was the case due to the second creeper blowing me up.

Thank you for the speedy response.