I'm sorry that this happened, but the way you handled yourself was good and hopefully promotes the image of responsible gun owners.
I worked in private hospital security for a year and a half in Oregon. There were no requirements on the size or type of sign required for private property. Simply put, if we told someone or had a sign stating practically any reasonable thing it could be enforced. Also, we could tell someone to leave the property without reason. Failing to comply with the above would result in charges of trespassing, and disorderly conduct. We never had an incident with a concealed licensed holder, but had other incidences that resulted in those same charges. Most judges around here don't care about what's not said, but what was said by both sides and most judges will side with the property owners.
We had lock-boxes for mostly unconscious patients that were brought in with concealed handguns. The way this security officer handled it should be fired. The security officer is a liability to others, and makes them seem to be a fly by night operation.
I don't know if this hospital administrator will follow through, sounds like he will, but I'm always hesitant to buy something and give them the receipt hoping I'll be reimbursed. I would instead just have them order it, and send it to you if at all possible.
If someone wanted to store their handgun in our lock-box, we would get another security officer, explain the clearing procedures (we had a clearing barrel), have the owner simulate the clearing procedures, asked the owner if they understood, and then have the owner sign some paperwork releasing us from liability (just for show). We would then photocopy their concealed handgun license, and start the clearing procedures. After the clearing procedures were completed, the owner would write down the serial number, type and the accessories that went with the gun (magazines, and ammunition), and it would be verified by both security officers. We would then store everything, including paperwork, in the lock-box that had two separate keys and give one key to the owner. The only other way to open the lock-box with one key was if it was our director of security. An additional log would be signed afterwords.
At anytime, if we didn't like the way someone was handling their firearm, we would ask that they leave the hospital. We would never touch the firearm, unless the patient was unconscious and it was confirmed by a doctor. Not only that, but we would require the doctor to document and sign a form attesting to this.
When the person would pickup their handgun, we would repeat the same thing but in reverse. We would then shred the photocopy of the concealed handgun license in front of person, and have them sign a release stating that they got everything in the same condition.
Every security officer received training on this, and the company who trained us was approved by our liability insurance company. I have yet see a better way of doing it - if you were to have turn-in procedures at all. Most of the time, we could just see people turn around at the entrance, go to their car and come back - no big deal.
Occasionally, we would get someone coming out of the emergency department wanting it stored because they, their children or spouse, were going to have an MRI and they wanted to be in the same room.
Again, I'm sorry this happened to you but I hope everything works out.