I was reading through the rules Q & A today and wondered about this one:
Q: My disc landed in a creek that has been declared casual. May I place a rock or a broken limb behind my mark, to stand on in order to keep my feet dry?
A: If you choose not to take casual relief up to 5m back on the line of play, then you must take your stance as you would anywhere else on the course. You are not allowed to move obstacles on the course to build your lie, or for any other reason, unless they are casual obstacles. If you do not want to play the lie as is, or take casual relief, you may declare Optional Relief or an Optional Rethrow at the cost of one throw.
Applicable Rules: 803.04 Stance, Subsequent to Teeing Off; 803.01 General; 803.05 Obstacles and Relief; 803.06 Optional Rethrow
The wording is a little confusing. Sounds like the answer to the original question would be yes, since sticks and stones are casual obstacles.