No need to soak them.
At this time of year, I'd get a 3 inch pot, use John Innes number 1, 4 seeds around the rim , and wait 2-3 weeks for them to come. If you haven't got a greenhouse, a warm window sill will do.

Some people do soak seeds before sowing, but only for 1 day. If you haven't got a greenhouse, a warm window sill will do.

For future years, they can be sown anytime between October and early February with the aid of a little bottom heat to get them going.

The ones you have sown, give them another week or two.
If still nothing, seeds have probably rotted. Tip the compost out and have a look is the only way to find out.

Catch up on one of the two episodes of Gardeners' World on BBC - Monty Drone was giving his opinion on this (it may have been the episode from 6 March so may no longer be on iplayer)

I'm wondering if three days in water has rotted them. I only ever leave them to soak for one night. I think I'd start again with fresh seed. The soaking quickens germination that's all. Some people Nick them as well. I did that once. I've only had a Propagator this year and they never failed to germinate before...either on a windowsill or in an Unheated greenhouse. Plenty of time to start again now, but do it soon.

Monty might be a good TV gardener, but when it comes to sweet peas I'd take the advice of true experts.

Advice I give comes from such people, and adapting their methods to suit myself.

None of them grow them the way Monty recommends in the videos I've seen him do.

I don't rate the mighty Drone at all - but I'm guessing that the GW researchers are up to the mark.

Soaking seeds is really for the US where it is dry in spring, after a dry winter. As per the above i just put the seeds into a pot and leave somewhere semi-warm and frost free.