If you notice the lack of complete cutting before you move the sign, you can re-cut that line and finish the penetration. Tinwhsiperer has posted very detailed instructions. Search “cut from line” and “cut from loop”. See his post:
FireControl Continue mid Code - Software / FireControl - Langmuir Systems Forum
On something you’ve already removed from the table, a Dremel with a one inch cutoff wheel and other bits can be used.