I am only guessing, but maybe try to see if there is, in mdadm, a command to scan and activate. THEN see about the LVM (if the md partition is type LVM, you may need to activate the md device first, then type the following:
# if the vgscan thing has already been done, type...
I once thought I LOST the setup on my drive, but I did not, so, it may be the data is still there. Maybe the assemble command is used for creation, and you just need to say 'Hey, activate this please'. I would advise you READ THE MANUAL PAGES so you can be ABSOLUTELY sure, because, like I said, I thought I LOST my partition completely. If this does not help, sorry. Hope it does