You could pre-measure your snacks into smaller packets, and take two with you. Maybe you eat just one; maybe you eat both. Either way, you'll know *exactly* what you ate.
Or you could take your leftovers home and weight the remains, then the difference is what you ate.
Or, sure, a food scale at work, why not? It's an extra expense but they really are very handy.
Goal 1 - break 200 (46 pounds lost)**DONE**
Goal 2 - leave obesity behind (BMI 29.9, at 185#) **DONE**
Goal 3 - BMI = Normal (154# or less)
| current weight: 169.0