Hopefully the result of the incident wasn't too serious -but- the post incident diagnostic all led to the same culprit - you had a poorly made servo extension cable between the receiver and the servo(s) and vibration loosened 1 until the servo was no longer receiving signal from the receiver.
Now there are plenty of ways to deal with this - you could:
Why not check out the slickest solution of them all - a safety clip built in to the servo extension itself! It's a flexible plastic, it won't snap if you bend it to remove the servo, you can bend it right back -and- it adds almost no weight to the overall setup.
Try a few and see - then when you realize you can't live without them, buy more 5 packs. Available in all the common sizes (15CM, 30CM, 45CM, 60CM, 75CM, 90CM, 120CM & 150CM). Want to buy in quantity for your whole club - I can handle those orders too.