Mixing personal funds with SDIRA

[Account Closed]

I have been thinking about this for a while. Please keep in mind that I am NOT thinking about doing this but am just curious as to how this is enforced. If I have 100K in my SDIRA, bought a property for 90K, paid 10K out of the SDIRA for the rehab and another 15K from my other LLC's funds, how would they even know that I used non-SDIRA funds for part of the rehab?

I could just add the 15K to the bid from another rehab and pay the contractor, I am sure the contractor does not care which account he gets paid from.