I've been creating a modded adventure map over the last three years and have finally decided to deal with an issue that I've been aware of for a long while. I'm trying to make it so certain items are undroppable quest items and keys that are using CanPlaceOn Commands. I put together this command as an example...
/give TRENADIX minecraft:lever 1 0 {display:{Name:"Asylum Key",Lore:["Escape the Asylum"]},CanPlaceOn: ["minecraft:iron_block"],PickupDelay:0,Age:-32768}
The point of this is that the player will instantly pick the item back up if accidentally dropped but it can still be placed in storage or placed on specific blocks. I set the pickup delay to 0 but that's not working fast enough.