Hiya Pat,
Welcome to TP.The anaesthetic and strange surrounding of a hospital would have made your mum confused. Often people with short term memory loss can 'cover up' when in their own environment, but when elsewhere the confusion shows.
The hiding things, and accusations about stealing are very common. The best thing is to try and change the subject, do not confront your mum. She cannot remember hiding them, she cannot find them, therefore someone MUST have stolen them. Logical, isn't it!?! Remember mum is entering a scarey world. Her brain is beginning to struggle to do the simplest tasks - putting her clothes on in the right order may take a lot of thought. Things are getting lost all the time. She may have to think hard about how to make a cup of tea. Things, people, places, words - they are all becoming less familiar. Do not keep reminding mum that she has asked the same question 10 times, try and answer it with a smile each time, as though it is the first.
Mum needs you to take this journey with her. Reassure her that she is OK, that she will be OK. Enable her to do as much as she can for as long as she can. She needs you to understand, and forgive, the aggression, because she is going to say things that will hurt you. She needs you to keep her safe, and as time goes on to make the right decisions for her.
Helena is right. If you haven't already got a POA, get mum to sign one - it will save you problems in the future.
Take each day as it comes, and make the most of it. Hopefully you have many more days to enjoy with your mum, even as the illness develops. It is not all bad!!
See if you have a local Alzheimers Society, they can provide support and put you in touch with other agencies. There is also the national Helpline, which can provide information and support.
Welcome to the rollercoaster ride of dementia - you are not alone, there are many of us on it with you.
Love Helen