What Excel does to long identifiers
Excel stores numbers as IEEE-754 doubles, about 15 significant digits. A 16-digit order ID or barcode is rounded on entry. When the sheet is saved as CSV, you may get 1.23457E+15 instead of the identifier.
What this tool will and will not do
It scans identifier-like columns and cells that match scientific notation. When the mantissa still has enough digits, it writes the expanded integer. When the mantissa is short relative to the exponent — typical of Excel\u2019s display form — it still expands, then warns that exact recovery is impossible.
Example
order_id 1.25E+3 1.23E+15
Output:
order_id 1250 1230000000000000
The second row is flagged: those trailing zeros are not the original ID.
Limitations
This is not cryptography and not interpolation. If precision is gone, the honest result is a warning, not a guessed barcode. Amounts that legitimately use scientific notation in scientific datasets should be excluded from the column list.