I Am Currently On Ursodiol And I Didn't Think I

I am currently on ursodiol and I didn't think I had taken it tonight (but I had) so I looked for it and put my hand into the couch and found a pill that looked similar and took it. After I took it I thought that it didn't look right. I checked my ursodiol and it wasn't the same. It was an oval, white pill with a letter and I believe a dash 11. Should I be concerned? I haven't taken any other pills all year and I don't know how that pill got in the couch and still be that close to the top.