Help needed to identify mysterious item found under the trunk floor

[Johan Touring]

Does anyone know what this part belongs and what it does?
Found it lying loose under the front of the trunk/boot floor when I loosened the screws and lifted it.
It was right next to a black box that I think is connected to the burglar alarm.
The car is an E39 Touring 525i 2002.
Johan

[430Scud]

That is the locking bar for one of the electrical connectors. Most of the wiring, when two connectors meet up, there is a plastic locking bar like that, that will slide over and retain both connectors together. You press a tab, and slide that bar back, to release the two connectors. One of your connectors is now missing that locking bar. Not the end of the world...I have found most of those connectors would likely stay together without it.

If you can find which one it is, you can probably slip a wire zip tie through and hold them together that way.