Oh no! There is no toilet paper!
We are running out of toilet paper here!
In overwork you modify a verb, whereas in overworked you have a compounded word with "-worked" not being a verb, but closer to an adjective and the "over" meaning "too much/in excess/overly". Indeed, the entire word (overworked) all the word is a adjective meaning "having to work too much" or in other case "something used to much" [an expression, a word, a cliché etc].
"toilet paper" is not used in that way, with "over". It´s not a natural way to talk in English.
http://dictionary.cambridge.org/pt/dici ... overworked