honeywolf -- I don't want to scare you, but just wanted to relate to you something that happened to me a couple years ago.
I couldn't get in touch with my parents. Finally, my dad returned my call and just said he and my mom had been busy. When I asked to talk to her she was out here or there, constantly. Finally, when I tried very very late one night and he couldn't make an excuse, I found out she was in the hospital, in ICU and the prognosis was very bad, but she had made him promise not to tell me because she didn't want me to worry. Can you imagine how scared and angry I was? She ended up being in ICU a total of 13 weeks, but eventually came home.
I hope your parents are just separately pursuing other interests. Good luck and keep us posted. I will say a prayer for them and you that this is all very simple and innocent.