Dad may have tens of thousands of dollars in cash, denying it exists in divorce?

Location: Ohio

My dad has been the bread winner the entire marriage. There are bank statements for years showing cash withdrawals of up to $1000 a month for years.

He claims that all of this money has been spent on various things such as gas, dinner, groceries, etc. and that he only has a few hundred dollars in cash.

The total amount is around $90k

Is there any way that a lawyer could potentially have him pay half of the withdrawals from over the years to my mother? We are convinced he has stashed all this cash somewhere but we have no clue where he could have possibly prove it or how to prove he does or does not have it.