Help with missing carrot seedlings

Please help as this is my first year of veg growing:

I sowed a couple of varieties of carrots outside in my small plot about 5 weeks ago. All was looking good with lots of healthy looking seedlings.

At the weekend I thinned them out as lots of them were growing too close together and then covered them with fleece straight away to deter carrot fly.

I went to check on my carrot seedlings yesterday evening and they were all gone. Every single one.  None of the other seedlings in the garden are gone (spinach, rocket, beetroot, radish, broad beans) so I can't understand what has happened to these.  Surely if it was the dreaded slugs (which are slowly munching their way through my winter gem lettuce) they would have taken the other seedlings?

Did carrot fly get them - do they eat the seedlings?!

Looking for some advice as I want to sow another batch but don't want the same thing happening so thanks in advance for any help.

Thanks - I guess I'm relieved it isn't something else I've done wrong.
Looking forward to my nematodes arriving but I'll try a few pellets in the meantime and might go out on slug patrol.
I hate slugs.

As a very happy coincidence the postman has just delivered my nematodes so I'll be applying those after work tonight.  Fingers crossed as I seem to have an unbelievably huge slug population in my garden. My Mum lives down the road and has none at all. So unfair.

have you looked in the bureau?

Do not jump to the conclusion of slugs too quickly. Could just as easily be wireworms, leatherjackets, cutworms, millepedes, symphalids, springtails, chafers to name but a few.

Time to do some detective work. Can you find any remains of plants? Have just the leaves been eaten? Have the stems been bitten or have bitemarks? Have the roots been eaten?

Have a careful dig around and see if you can find any bugs in the soil. Take a trowell full of soil and spread it out on a sheet of paper. See if anything starts moving.

Probably slugs. Put a few slug pellets under a plastic bag and anchor it down with stones/earth. If there are slime trails and dead slugs it is them.