A hint for future players. It effected me and I don't know it it's a bug or not.
When I first went into the interogation and was given the choice of either John or Sulley, I chose Sulley and then later wasn't able to pick up the coffee mug from Davies office. I went back to a previous save and chose John and was able to.
It's not a bug.
Things change and puzzles change depending on the decisions made. There's about 8 places where changes affect outcome of things.
For example: Answer to Davies incorrectly, the game continues, but her email to Erica changes. Or, don't open up to Rose --it won't be so easy to get John's item. Same thing with Sully/John, the projection points are different.
hope that helps.