This will always be a problem if you let techs enter without the resident present.
In your case I suggest you ask the resident to provide your office a copy of the police report and ask your techs. Of course they will all deny any info. Talk to the scheduled tech individually. Yes, some steal but he/she will deny everything.
Later, respond to the resident that you did indeed talk with your staff and investigate, but no one has any info about the missing items (of course!) and suggest she submit this to her renter's insurance.
If the item was inexpensive, I would offer to pay for it in the interest of maintaining goodwill and to end the problem. If the problem liingers it will cost hundreds in time and hassle.
Wanna be right or rich?
Now the real answer:
We changed our standard policy to "no entry without the resident present".
In reality, we changed this for our own protection, not just from claims of theft, but more importantly for our liability and our personal safety.
Entering without the resident present might have been OK in 1962, but not anymore. Now it is asking for trouble, maybe even getting shot.
Our guys used to bang on the door 2-3 times before using a pass key, crack the door open and yell MAINTENANCE 2-3 times before entering. Even with all that ruckus, 20 minutes into a repair a sleepy eyed someone would appear from a bedroom and surprised by our presence. Often the girlfriend called in the request and the night shift boyfriend new nothing about us coming. He was fast asleep and never heard us banging and calling out.
What if he had a gun?
This was not a concern for our men, almost a joke, but it came to a head when we shifted the quarterly maintenance/safety checks to the lease manager - new, young, pretty, and small. Her job included checking the smoke detectors inside bedrooms and she walked into several rooms with men sleeping. That ended that!
People can be crazy and we no longer put our staff at risk of harm.
We setup our website service request page to allow the resident to set their own appointment time. They love it!
If they call in, we call back and set up an appointment. Side note: they provide us a cellphone picture of the problem helping the tech prepare before the appointment!
I know this sounds more tedious, but the residents like it better this way. They feel more respected, feel they have control over their home, and we look more professional. The techs like the appointments - helps keep their day moving.
Hours: we staggered the staff schedule so one tech is on duty until 6. He covers the "after 5" appointments.
Keys: only the maint super has a master for emergencies. No more checking keys in and out, HOPING the tech is honest and HOPING he did not make a copy.
If the resident misses the appointment (happens!) we leave a courteous note and ask them to resubmit/reschedule and we'll give them top priority.
Plus MY life is easier because there are no more complaints about "he took my stuff"!
Best of luck!
-Brad 20,000 Grayson