First off - well done, the lamb is still alive
Next - are you certain the lamb isn't suckling when you are not there? Is its belly empty? Often they are suckling on the quiet, so are not hungry and therefore not interested. And/or, they've emptied mum out, so she's moving away as she has none left.
To see if it's empty, hold it up by its front legs with its spine against your legs. Around and below the belly button - if it's rounded / convex, the lamb has fed. If it's hollow / concave, the lamb has not fed.
If you're still not sure, you're through the first 24 hours now, so although of course it still needs to feed, it's not so desperate. So I wouldn't tube it now unless you are positive it is empty and you cannot get it onto the teat. If you're still uncertain come bedtime, feed it no more than 50ml just to give you peace of mind that it'll survive the night.
A lot of people say never bottle feed a lamb that's to feed off its mother, but IME it can be helpful to teach the lamb to suck, then transfer that learning onto mum's teat. Once you see it greedily sucking on a bottle, you know it knows how to suck and it has an appetite, so then you can renew your efforts to get it to latch onto mum.
When you wake the lamb up, does it get up and arch its back and stretch? If so, it's feeling fine