Disorientation. Nothing is where it should be. I have knitted patterns written for dpn on circs and used markers to mark the end of each set of stitches that would have been on a separate needle. What pattern are you using? The 'last 3 sts on the needle' would be, I think, the last of the heel stitches on your circ. If you can sort out in your head which stitches are where in relation to what you're used to, I think it will make sense. Maybe because I knew you were doing top down socks in your other threads, I knew what you meant in the title. You can edit it if you want to. You might run down a pattern written for circs for comparison. The numbers of stitches might be different but the way to do it would be the same.
Happiness is catching that dropped stitch while it's still fixable..