How would I check if an item is thrown into a fire?

How would I check if an item is thrown into a fire? I right now use execute as @e[type=item,nbt={Item:{id:"minecraft:wither_skeleton_skull"}}] at @s if block ~ ~-1 ~ minecraft:fire run say "Skull detected!", however this doesn't seem to work and I've heard that nbt detections like this are not very good for performance, so I was wondering how I should check if an item is thrown into a fire. Perhaps it's important to note that i don't want to detect items with custom data's I just want to check for regular items like a wither skull.