battery drained again

[jaima]

For roughly six months I thought I had eliminated the battery drain problem!
today I went into a shop with the wife sitting in the X5, five mins later she
phoned me saying that there was a bleeping noise coming from the car, I came
out straight away and the hazards we flashing as if the alarm had been activated,
Twice in the last three weeks I had to get the AA to come out
and jump start the battery/X5, the mechanic hooked up his meter on both
occasions after getting the car started and tested the battery and alternator,
both battery and alternator tested good.
could the alarm be activating by itself???
a neighbour across the street told us he has seen the hazards flashing a couple of times late at night,
the volume from the alarm is pitiful to say the least, none of us heard it in the house if it did activate itself.