My question involves criminal law for the state of: California
I attend the Institute of Technology in Modesto, CA. I am a student in the Culinary Arts division. I am currently a member of a team participating in a culinary competition tomorrow, Friday, July 24th. At the request of my teacher Chef Jenny, I came into school prior to my class period today to practice for the event. This is the first time our team had practiced while the morning class of culinary was in session.
My iphone was out of power due to use during a school field trip to San Francisco the day prior where I had to direct a group of students where to walk. I would have normally charged it after school, but was asked to stay after by Chef Jenny to prepare for the competition until midnight. I needed the phone to have power so that I could catch up on personal responsibilities that I would have taken care of today, but I could only hope to sneak in between practice and class due to the sudden change of schedule. So this morning, I requested from Chef Jenny that I be allowed to charge my iPhone using her teacher's computer in the Mod 2 classroom. She agreed that was ok. I plugged it into the usb port on the back of her computer and hid the phone itself in a vertical stack of files sitting up next to it. I let her know I had hidden it to avoid theft. She agreed it was a good idea.
After our competition practice a few hours later, she and I returned to the Mod 2 classroom and found that only the white iphone cord remained. We searched all over for it but it was gone. One of the Mod 2 students who had remained in the classroom told us that Chef Joe, their instructor who sometimes shares the desk, had found the phone, held it up to the class and asked whose it was, followed by saying "I hope it doesn't get stolen" when no one claimed it."
I went to find Chef Joe figuring he had confiscated it or taken it to a lost and found. When I approached him, I was shocked to find out that, he simply put it on top of the desk and went back to the kitchen when no one claimed it. This confirmed someone had stolen it.
I spoke with the director Chef Paul about the incident. He told me that I could file an incident report with the school and that I should call my phone company right away and suspend the account just in case the thief made a bunch of erroneous calls. He also suggested I call in a police report. He assured me that come Monday (the students in Mod 2 only have classes Monday-Thursday) he would arrange to speak with all of the morning students about the phone and try to get it back.
I used the office phone with permission to call the phone carrier and suspend the account as well as file a police report.
My friends have suggested that since Chef Joe very plainly let everyone in that class know that there was an expensive phone charging under the desk, then left it out on top of the desk for anyone to take that he or the school are liable to replace the phone. That the responsible course he should have taken was to first ask his desk mate Chef Jenny about it and secondly to take it to the director or lost and found.
Is the school and/or Chef Joe responsible for replacement?

