When you lock a map in Bedrock Edition by using a glass pane with a cartography table, you get a locked map item that has its own icon. This is not the case in Java Edition, where the icon for the locked map doesn't exist.
MC-240904
Parity issue: Locked Map inventory item icon does not exist
Resolved
Invalid
0
This is not a valid parity issue, as it predates the Buzzy Bees update. This texture was added to Bedrock Edition beta 1.13.0.1, according to the wiki.