Until the cause of:
a) the initiation of the ejection and...
b) the failure of the main parachute to deploy....
...are known, speculation as to whether a mild overnight medication had any effect is inappropriate in my opinion. It
may become relevant, but right now, it's not.
I have never, in 31+ years flying in the RAF, seen a ban on mobile phones in the cockpit. They should either be in Flight Mode or turned off, but the mere presence of a mobile phone, turned off, in the cockpit, is irrelevant. Perhaps the army were finding their crews were actually using them on the flight line.
Clearly they didn't have the special mobile phones that surgeons, movers & the AARC have.