If my client's company was got scammed $2,500, how should I record that loss in quickbooks? Thanks!

Hello there, Ethan Zhou.

There are times when a supposed income becomes a loss, you can write off bad debts in recording them. This way, the invoices will be cleared out and the net profit will be reduced. 

Here's how:

1. Review the Accounts Receivable Aging report.
2. Create an account for bad debts.
3. Create a product/services item for bad debt.
4. Create a credit memo for the debt.
5. Apply credit memo.

These steps also have sub-steps, please refer to this article to see them: How to Write Off Bad Debt.

Also, I'd suggest consulting an accountant  to be advised on how to record the scammed or loss amount. 

I'd be right here if you need more help.