Should storyboard with a company if no contracts has been signed?

I may be potentially offered an opportunity to film 2 ads with a dog company. We spoke on the phone once and they told me they wanted me to create and storyboard and idea and then send to them. Im still learning in this field, so I am kind of worried that if I send them my ideas they can just go with someone else. Should a contract be signed or am I just being suspicious. Thank you.