Missing data after attaching .mdf file
Did you run a DBCC CHECKDB on the 'recovered' database? Is is consistent? 

Your case doesn't hold water though. In theory the most you could had lost was the transactions present in the log (LDF) but not flushed in the data (MDF). That would amount, at most, to the dirty pages not flushed since the last checkpoint, which would be minutes of data loss, definitely not days. 


  I'm also sure that it is the most recent .mdf / .ldf that is recovered and sent.


Being wrong on this point would be, by far, the simplest explanation. Other explanation is that you deleted the data after attach, which is kind of silly. Or the recovery returned a corrupted MDF that is missing data, but that would fail with corruption errors when trying to query it. I would double/triple check again that is indeed the latest mdf/ldf that was recovered.