1998 Chevy Venture Power Steering fluid

Hi,

I was getting ready for a trip tomorrow and was checking my power steering fluid when I dropped the cap. It was wedge at the bottom of the engine and I tried to use a stick to flick it so it would drop out and needless to say it is lodge somewhere in the metal of the car. Until I get a replacement do I need a cap? I stuck a paper towel in the top to try and prevent moisture from getting in. Will this work or do you have a better idea.

Thanks much.