A Drobo on a server should be configured for RAID 1, 5, or 6 redundancy so that you do not lose data if a single drive fails. Accordingly, that missing document should have been written to multiple drives in the Drobo, which also should have had Time Machine configured to provide another level of document redundancy and recovery. Have your administrator check again for that missing document. Assumption: Your Drobo is using Apple's HFS+, and not Microsoft NTFS filesystems with client NTFS third-party driver solutions.
Pages v5.5.2 writes temporary information into the following variable location:
/var/folders/letter_/30alphanumeric characters/capital letter/
Each boot cycle will clear this location, so looking for temporary document content is futile after a reboot. I used opensnoop in a terminal aimed at the Pages v5.5.2 process to track all filesystem access during a Pages launch, file creation, save, and quit.
Another way files can appear to vanish is when a document is saved to iCloud gen 1, and Yosemite's iCloud Drive is enabled. The documents are converted to iCloud Drive (gen 2), and are no longer available to systems not running iCloud Drive.
Do to its feature limitations (compared to just about any other word processor on the market), and Apple's limited commitment to its improvement/bug fixes, it is hard to say what constitutes expected behavior, bugs, or just plain crapware. Pages v5 (any release) is not professional/business grade software, and using it in this capacity constitutes expensive, and unacceptable risk. The reviews in the OS X App Store for this product speak volumes to this paragraph.
