Saudi aircrafts hit by missiles

Janes’ has confirmed that a Saudi F-15 was recently hit by a missile:

A Royal Saudi Air Force (RSAF) F-15 multirole fighter was “intercepted” by a surface-to-air missile (SAM) while flying over northern Yemen on 21 March, but managed to complete its mission, Colonel Turki al-Maliki, the spokesman for the Saudi-led coalition, said later that day.

http://www.janes.com/article/78774/saudi-arabia-says-f-15-survived-sam-hit-over-yemen

AFAIK the F-15SA have the “common missile warning system”; however this is also being installed on the older F-15S, presumably with most a/c finalized by now(?):

http://www.deagel.com/news/Saudi-F-15S-Fighter-Jets-to-Get-Digital-Electronic-Warfare-and-Common-Missile-Warning-Systems_n000010217.aspx

In addition the Saudis also fly Typhoon, which has DASS with integrated MAWs that should trigger flares.

Why don’t they use Typhoon’s, F-15SA and upgraded F-15S exclusively in Yemen, given the risk of SAMs? Or perhaps the pilot forgot to turn on the system?