Is it obligatory to inform one's friend about what happened regarding the destruction of the check and the non-delivery of the amount, and is it obligatory to give a sum as charity by way of expiation if the transaction cannot be found with the company?

The check is a trust in your hand. If a trust is lost without negligence on the part of the trustee, there is no guarantee for it. However, your destruction of the check due to negligence makes you negligent, and negligence concerning trusts, if it leads to their destruction, necessitates guarantee. If you are unable to recover the money from the company, you must repay it to its owner unless he forgives you. If you do not know the exact amount, you must take a precautionary measure. You are not permitted to give it as charity unless you are unable to return it to its owner after thorough search and investigation.