This situation happened with my grandmother a few days ago. Even though older people are forgetful I do not believe my grandmother has misremembered this situation or confused herself.
She wrote a $50 check to an association and it was never received. She contacted the bank and they said that the check with that number was processed by a grocery store for ~$300.
My grandmother has never spent that much money at a grocery store and rarely ever writes checks in person. The bank went through her recent transactions and found that that check number and the previous 3 check numbers had also been processed for near $300 to places she had never been.
She dropped the checks in the mail box for certain associations and companies days previous.
How would someone rewrite her checks that were marked in pen?