Sister kidnapped mom and took over POA. What can I do?

My mother is in end stage MS with stage 6 dementia (she knows the year, president etc... so can't be defined legally incompetent..but could not tell you what she had for breakfast). I have been her FT in home caregiver since 2010. In 2008 my mother executed a POA and advanced healthcare directive putting me in charge with my sister as backup. In 2012 I updated both leaving a personal trusted friend of 27 years as 2nd in charge, cutting my sister out in response to her irrational behavior (involving false accusations to adult protective services and the police; which have been ongoing since 2012.) I have provided in home hospice care 5 days a week as well as a private nurse 6 days a week during this time. I have been paying all the bills, taking her to dr. appts, living here at the house (which is in both my mother's and my name on the deed).
Long story short, last weekend the nurse was not available, so I enlisted my sister's help. She was supposed to come to the house late Friday after she got off work and spend the night and help Saturday. She showed up unannounced (per usual) mid day Friday and said she was going to take mom to her house for the weekend. Fine. I provided her the van to transport mom with the understanding that mom would be back Sunday. Saturday she called to let me know that she would be keeping for the week as she would be on vacation (she worked all week leaving the housekeeper in charge of my mom). The following Wednesday my mother called asking me to bring her home.
Now as I understand, when she picked her up on Friday they went straight to the bank where she unknowingly put my sister in charge of her finances. I have had no contact with my mother except that Wednesday. My sister will not respond to my calls, emails or texts messages. I had the sheriff's dept do a welfare check on Thursday - they said she appeared ok. I've requested adult protective services visit and inquire as to my mother's wishes; as I believe she is under undue influence and distress with my sister's actions.
I have contacted both police depts (we live in separate counties) stating that I think my mother is being held against her will. I have contacted the bank in person with my 2012 POA, who stated that my mother 'appeared coherent' during their visit, therefore her verbal consent out weighs my POA.
Long story short. I have no idea where my mother is, I have bills piling up w/o any access to her bank accounts and I'm worried that my sister has already executed another POA and has moved her out of state.
I know I need to contact the original elder attorney who executed the 2008 POA and see what he can do legally. I am avoiding going to probate or family court as I assume they will only appoint a 3rd party guardian and/or conservator, which will only deplete the dwindling funds for her care at home. I will contact both police depts again on Monday to report my mother kidnapped or missing and the van stolen.

I am highly stressed regarding my mother's physical and mental condition. It was her wishes to remain here at the house for the duration, which is the reason I left work to become the live in FT caregiver, as my sister thought putting her 'in a home' was a better idea. Any ideas? I feel stuck and helpless.