Grandma's social security put on debit card

My mom went to Kentucky to get grandma to take care of her but other people new all her information.so when mom brought her back to michigan the cops in Ky. Got debit card and gave to my mom.when mom got back to michigan she opened account for grandma to have social security direct deposit.someone in Kentucky had ordered a new card and cashed it.the cops down there says there's no way to prove it was cashed there.seems like they could see transactions from card on record somewhere but it looks obvious they just don't want to get involved? So my question being that social security is Federal government who should get involved what type of law. She draws $1900 that's got to be like grand theft?

Also forgot to mention my grandma is 93 she's got dementia in 3rd stage.my mom called debit card place and they can't do anything until they talk to grandma when mom puts grandma on phone with them she can't answer the questions do to the dementia so the card place won't do nothing until she can answer there questions obviously she can't do.what a joke

Your mother should investigate being declared your grandmother's legal guardian or conservator.
To do that she should discuss the process with a KY lawyer, as your grandmother lives in KY.
Your mother might also want to try and get a letter from your grandmother's physician indicating her medical problems.
She can then use that letter to contact Social Security and attempt to be appointed her mother's "Representative Payees".

If your mom becomes her mom's "Representative Payee", it'll be easier to get this sorted.

This link to SS discusses the RP process:

http://www.ssa.gov/payee/faqrep.htm

If your Grandma has dementia where she can't handle her own financial affairs, your Mom definitely needs to take action to become her guardian or conservator.