Ok I am the lowly fire guy with not many initials after my name.
Here is my 3 cents. (used to be 2 cents but there is inflation).
What type of sprinkler head are you talking about?
All heads, ESFR, Deluge, Residential, each head has it's specific characteristics, their own testing protocol, their own installation procedures and their own testing procedures.
What type of head it is other than a glass bulb? The following questions need to be answered.

What is the temperature rating for the head,it it a side wall, pendant or upright?
What was commodity was it protecting?
What is the environment that the head is installed in to protect, Warehouse, Retail, Residential, Manufacturing, Warm storage, cold storage, dusty, spraying.
Do you have the ITM records for this system? Were ITM's done for this system?
You can hypothesize all you want but in all these post I am seeing no hard data. The questions above are the standard questions I ask when doing an investigation on the public side. Finally for all of the initials you folks have after your name have you ever considered calling a engineer from a sprinkler manufacture like Tyco or Central States?
Just my 3 cents.

Mark Spoo Fire Marshal Fire Investigator RN EIEIO
River Grove Fire Department