Part of your job as a parent is to introduce realistic expectations for your child when the world does certain things. Mommy, Daddy or both will probably need to be inaccessible for protracted amounts of time in order to work, even if one or both don't leave the house to do so. I kind of think 'vanishing' dodges that, at any age .. but we all lose idealism when our kids get really upset.
Depending on the age of your child, books like this one can help a bit, but what works the best (if your child has reached the age of conversation) is not excusing your absence, but explaining it. Turn on a light switch, for instance and explain that if you don't go to work, the light might not work for very long. Take out a box of pancake mix, make some and explain that if you did not go to work, there might not be so many pancakes. Then involve your child and let them come up with ways to help you go to work, or vanish in your home office for hours.
The trick is not to instill some sort of trepidation in the child, they should not be worrying about your job, so take special care to discuss work related hiccups when your child is not around. Make it a positive thing. Tell your child how what you do makes something better, talk about your work friends, bring home random office supplies as gifts and make it a point to introduce 'special' events when things go well at work.
Again, this depends entirely on the age of your child, but I'm quite sure bits of it could be adapted to fit your current problem :)