What is this (on my tow mirror)?

[mphst15]

Anyone have an idea what this is on my driver's side tow mirror and if I am missing a piece:

https://goo.gl/photos/TKZaDDgAcGsxnrg3A

To me it looks like something should slide over that post as part of the puddle light assembly but I'm not sure...and of course I never noticed it before.

Thanks in advance

 

[SportyJames]

I like how you painted your truck to look like a barn. Ambient temperature sensor maybe.

 

[quietpeen]

pretty sure like mentioned above it is the outdoor temperature sensor

 

[00R/T]

pretty sure like mentioned above it is the outdoor temperature sensor

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