Any one of us here who has raised bottle lambs has been where you are and can empathise.
It does get, if not easier then more bearable and worth it overall, for most of us, but there are bound to be many who decide that the potential for heartbreak is not for them and who don't do it again.
I'm sorry you were only able to get the 1, it would be a help to you to have the other 3 to continue to rear at this point. It's very hard to lose the only one you've ever had.
(I assume the farmer had a good year and no other cades to spare, so that's good for them - but no help to you at this point.)
It will feel a very long time, just at the moment, until next spring and your own ewes having lambs. But hold onto that thought, and it will be here before you know it, honestly it will