Use a pump. Siphon is to “suck.” A pump sucks and then pushes.
BTW - 3,000 USG of gasoline = about 24,000 lbs. or 12 tons. I think he may have been taking less at a time.
The 3,000 - 10,000 gal. are estimates of what he stole per week. So all he needs is a 500gal tank in his tralier.