Possible houses in Oblivion?
Solution 1:
The unofficial Elder Scrolls wiki has a good database of the traditional houses (like those that can be purchased in each of the major cities) as well as a list of the houses that don't count for your "houses owned" statistic. The wiki also has a complete list of non-respawning containers; normally, the contents of each crate, chest, and container gets reset and randomized every 3 in-game days.
Here is the page for houses;
Here is the page for non-respawning containers
If you can't find your stuff stored in either the "free" houses, or the safe containers, you may simply be out of luck, pending a burst of sudden remembrance.