Application of article 120 in case of a mistake by the employee

Hi.

I am working as an engineer. I am preparing BOQ for the project and I will forward it to my manager for verification and he will make a final quotation and send it to the customer.

Unfortunately, I did a small mistake while making the BOQ in the Tender Stage Project and forwarded it to my manager for further procedure. He has not noticed also the mistake.

After a couple of months, the main contractor called for a final discussion. That time we cross-checked the BOQ again and I found this mistake.

I informed my manager that we missed this quantity which will increase the project cost, so we won't be able to meet their target. He shouted at me because we lost this project.

I will take the necessary action. I just want to know if Article 120 is applicable to this issue.

Please advise.