The engineer obviously nuked the partition table, but if that's all s/he did, no data has actually been deleted or overwritten.
For quite some time, partitioning tools have defaulted to starting the first partition at sector 2048, which represents a 1 Mb offset from the start of the drive. Unless this drive was originally partitioned using an ancient tool, the creation of a GUID partition table would not have overwritten any partitions.
If you can reconstruct the original partition layout, the file systems and associated data should reappear.
Edit: I spoke too soon. I see now that the engineer also created a partition with an XFS file system. That would indeed overwrite the existing file system on the previous partition. Time to restore from backups.
Last edited by Ser Olmy; 12-12-2014 at 12:55 PM.