From the looks of that the drive's partition table was corrupted now resulting in seeing unallocated drive space rather then an existing partition. In other words partition recovery time is what you would now need in order to locate and recover files from an apparently non existant partition.
Just hope you won't need the Dr.FreeNightmare to recover them better known as the free Fedora based Dr.Freeware data recovery program that literall renames everything it recovers from a drive into ??? many folders with names like recover_1, recover_2, etc. I pointed out to someone else lately with a similar problem.
This is another reason why custom installing programs to secondary drives leads to disasters! If you are not able to recovery anything from the drive you will need to reinstall all programs as well as suffer the loss of all the files you were storing on it. Not good!
The price tags on most softwares that can recover entire partitions when the MFT is broken typically run at about $70 as well when shopping around to price them. The demo versions won't work! A good number were tried out recently on an older machine when the partition table was lost and the drive appeared empty just as you now see that one.