If a player wearing a backpack dies, then presses the title screen button to quit the game on the "You died!" screen, and then the player joins back and respawns after returning to the main menu, the backpack they were once wearing no longer exists (they are no longer wearing it and it is not dropped anywhere). Running Forge version 14.23.5.2838, mod version 1.0.19.19. Traveller's Backpack is the only mod installed. This happens in Singleplayer and in Multiplayer as well.

for me its the same when i just click respawn

Same for me :/

for me its the same when i just click respawn

i only tested it with explosives, when placed on the ground the backpack survives but if i wear it it disappears