If that paper only has your signature, it can't be done. If the company denied it at that time, you have no evidence to prove that the company gave you a long vacation. So what you are worried about is likely to happen. But you can make a recording evidence with the company leader. The content is to ask the company leaders to confirm that the company really gave you a long vacation, and that paper was also signed by the company. This is more secure, otherwise disputes will be very troublesome in the future.

I hope my answer is helpful to you. If you want to know more, you can visit the website of Yifatong for consultation.