Need to identify what this is, and where it goes

[Multibeemer]

This is really strange. I was in the process of moving my 03 4.4i's windshield washer reservoir out of the way as one of the early steps in the procedure to replace my car's valve cover gaskets. As I was struggling to disconnect one of the connectors that I thought went into the reservoir, the thing in the photo below came out. I didn't catch what it came out of, and I can't figure out what it goes into, which is weird, considering how big it is (3.5" total length). Can anybody help? Thanks.