Unlike marijuana, cocaine has a very short life-span in the body. Your estranged wife would have either had to have anticipated you'd be injured on the job so she could sneak into your house 24 hours in advance to dose your food, or know when a random drug screen for you was coming up and do the same, or be sneaking into your home on an on-going basis to put cocaine into your food.
As Sockeye said, she'd be blowing a whole lot of money on all this cocaine and you'd be hard pressed to miss the immediate effect if you ingested it. What you are suggesting doen't make a whole lot of sense.
A person, who is nice to you, but rude to a waiter, is not a nice person. (This is very important. Pay attention. It never fails.)