@SweetPepper, the locked door policy at home's first home was something she tried to circumvent. Mum hated the thought she couldn't get out and I understand that. The home encouraged me to take her out for coffee and though I was loathe to do that at first she did actually enjoy it when we did go. This stage of dementia is a tricky one, as your mum is obviously still pretty aware of a lot of things, but totally oblivious to the fact she can no longer live independently. It is very sad when things do move on and the person with dementia becomes much less aware of things, but in some ways it is, if not easier, at least less stressful to cope with.
Like
@thistlejak's mother in law the home gave mum things like photocopying to do or put on her favourite films to distract her. It's early days and there will probably be various similar incidents, but a good home should be able to cope with them.