I don't know what the voles are like in your area, but here they are pretty small and their tunnels are often close to the surface - at least in winter or after winter I have found the evidence of their root munching. Anyway the hole by your foot looks more about the size of a rat hole I might see in my compost. A rat would not be attacking your tomato plant roots but may be planning to harvest them one by one as they get just ripe.
Either way, if your trap is not working, the solution is to dig up the area where the hole is found in such a way that any tunnels are destroyed...