Sorry to hear of your misfortune.
When I was a young Ops lad at a grass strip airfield we had a number of aircraft robbed of their fuel.
We didn't have CCTV in those days so I borrowed some NVGs off a friend and spent the next couple of nights staking out the airfield with a PC remaining in the local area awaiting my call should the culprits turn up.
As luck (bad) would have it, the NVGs were prod-all use as there was thick fog both nights. It's pretty spooky being on an airfield, out in the middle of nowhere in the dead of the night, especially when you can barely see your hand in front of your face.
On the second night at about 2am I heard a noise and thinking it was the thieves, cautiously made my way out of the unlit clubhouse to see if I could spot them.
With my heartbeat up to a gurzillion beats a minute (I was convinced they must be able to hear it) I crept towards the noise. A moment later I bumped into something and, flight or fight instinct kicking in, jumped about four feet in the air and was about to smash the 100m sprint world record when out of the fog materialsed a deer, who leapt even higher than me and made off into the gloom.
Well that was enough for me, so I radioed the PC and told him I was going home. No amount of overtime was worth the strain it was putting on my ticker.
Police picked up the culprits a couple of days later when they raided their caravan park for some other reason and found a drum full of Avgas and the pump they'd been using to drain the aircraft. Think they'd been using the fuel to power their motor bikes.
Can't recall if we topped up the resident's aircraft, free of charge, but suspect we did.
With the price of CCTV being so low these days I can't see any justification for not installing them at every airfield / farm strip - it's not only useful for catching theives, but also smugglers doing midnight flits in and out of airfields under the illumination of a harvest moon (but that's another story).
I'd definitely let the local Plod know of the theft as more than likely they'll have an idea who the cuplrits are. They did in our case but either had to catch them red-handed or find some other justification for getting a search warrant, which luckily they did.
Regards, jez