Don't leave them out in the garden. Start your seeds indoors and when they reach a decent size, gradually acclimate them to the outdoors. Always plant more then you really want because not all will make it. Yes, most likely a squirrel or something that liked to dig. Sorry to hear this happened.

As you'll not likely get rid of squirrels give them a better food source & some drinking water. They dig up roots & bulbs more because they're thirsty than for food

I'm willing to bet that it's field mice that are the culprits.
The mice can actually smell the seeds. One upon a time gardeners would coat the pea and bean seeds with red lead powder and parafin. I would germinate somewhere safer or perhaps a covering scent with a sprinkling of chili powder, garlic or crushed mothball.

squirrels , mice, pigeons, blackbirds, rooks, etc will all do this. cover with a wire 'cage' to try and keep them off.
the squirrels do this in ours and drink from the pond so its not thirst in my garden!

Thank you all for the great ideas I’ll try to make sure the next lot are better protected!