If the soil was overly wet and cold, then they could have rotted. I am not expert, so maybe others will have other ideas

Ditto. Beans can rot very quickly in cold soil. Is your location Denver? If so, you soil is still too cool for beans.

I agree with both. If your beans were white seeded, they are particularly prone to rotting away if the soil is too cold and damp.

I you want to make an early start or want to be sure of germination, it is possible to sow indoors and transplant. Not sure whether you sowed in pots and placed these in the coldframe, or whether you sowed directly into soil inside the cold frame. If you sow in the cold frame the better option is to place pots into the cold frame.

By now sowing outside should be more successful. However if you have any doubts that the seeds you have may be old or have lower germination for some other reason, you can still sow indoors and transplant after the true leaves appear.

Or... pillbugs. Mine eat black beans with great relish. Freaky. I sowed a lasagna bed with maybe half a pound of beans and just sort of hand-scattered and then topped off with compost (being lazy, it's just a cover crop more than anything else) and didn't put down any bait. They live in the not-yet-decomposed layers and get quite fat and plentiful on my beans. I have only four plants now.

My bean seeds keep getting dug up by my resident squirrel...why does he torment me so!?! I planted yellow and purple wax seeds a couple of weeks ago. The squirrel consistently goes after the purple seeds and sprouts. We've been playing this game the past 2 weeks where he digs up the little sprouts during the day and I replant them in the evenings after work...grrr...my husband says it's my fault for planting a buffet - but the little nut digger doesn't even eat them!

Squirrels are good from a garden too. Be careful you my get arrested for baiting wildlife. I just planted my beans and got a good shower they shoud be up pretty quick. Planting beans too deep can cause problems too.

No regrets, are you out there? Pillbugs eat all my germinating beans all the time and even seek them out in the greenhouse, no way to transplant even! You say "bait", what works for you? What I've done, all of which are a pain, are beer traps, diatomaceous earth, smashing, removing every single dead leaf on the ground immediately, never having damp soil at night, and generally keeping things dryer, no brush piles or compost near growing areas - anything else? And still they find my beans!

Control of pillbugs, ATTRA suggests two remedies. See link

Control of cutworms: see ATTRA's site which lists numerous, including Beneficial nematodes called Steinernema carpocapsae

Manufacturer: Becker Underwood, Inc.

Trade name: Millennium

About squirrels: Max have you tried laying down a good amount of used coffee grounds (free at Starbucks)? I've have filled many a chipmunk hole with UCGs, and the little rascals move!!! The grounds are also (mildly?) effective against slugs, so far as I can see. The experiments go on....

Here is a link that might be useful: ATTRA: pillbug control

ppod, thank you for the ATTRA recommendation link. Researching through it I learned that the EcoExempt IC requires a minimum $80+ commitment to test it, and dirt dr. test of it on fire ants was less than promising (quick knock down but no residual effect so you are constantly reapplying expensive product all over yard wearing respirator in sun yuck). Back to diatomaceous earth - which my personal experience is works great on lots of stuff although so far less than great on flea beetles and pills - but researching the EcoExempt product learned of the dust applicator DustinMizer ($35). I can certainly see where my DE hand broadcasting could be improved both consumption and application/effectiveness-wise so I've ordered one of those and will be testing it on the pernicious pills.

Follow-up: I purchased a Dustin-Mizer diatomaceous earth broadcaster and am using it with great and rapid reduction in pillbug populations, allowing me to grow beans at last! It has to be used frequently though (every week or three) and is a hand-hurting, nasty, time-consuming, mask-wearing job. So I'm interested in a non-manual crank alternative.