While, technically, it's possible, realistically it's unlikely. Usually the things that will cause a router setting to change without requiring the users approval are, 1) power failure which causes the router to fall back to default parameters.
2) system updates sent by the manufacturer of the router via internet. Please note that these updates usually require your acknowledgement in advance.
3) a virus that has gotten through your firewall and anti-virus protections.
You should be able to determine which (if any) of these are applicable to your situation. If none of them apply, then I can't think of another reason for the settings on your router to have changed from the last time.
Wouldn't hurt for you to go in and double check that the settings haven't been changed (if you can recall what they should look like, that is)