The reconciliation screen should have tick box up near the top right corner to show or hide correcting entries.  It is usually easiest to do the reconciliation with 'show corrections' turned off, as the screen is much tidier.  You shouldn't need to see correcting entries, because Sage is supposed to automatically clear both sides of the correction for you.  However, every once in a while, Sage only clears 1/2 of a correcting entry, which throws the reconciliation out.

So, turn on 'show corrections' and see if you can now see your problem entry.