The post-it on the door

A post-it appeared on the office door saying "back soon". Nobody knows who wrote it or whether they're back yet. Some clues in this case come as riddles. If one stumps you, a hint will solve it. Four people and one piece of evidence: one person per row, one per column. Whoever is left alone with it in the same room is the one you're looking for.

Suspects

• Aurora, the handwriting expert hired by the party: She studied the post-it's handwriting for three days. She concluded it was written by hand.
• Bento, the floor porter: He walks past the office door twenty times a day. He never read the post-it, because it isn't his.
• Celeste, the MP from the office next door: She says she heard noise at two in the morning. At two in the morning she was at home, but she heard it anyway.
• Delfim, the copy room technician: He photocopied the post-it for the file. The copy came out more legible than the original.