I have a Chinese Z Visa for 30 days but I went to Hong Kong

I was issued a z type for 30 days and with only one entry. I took a day trip to Hong Kong, but I couldn’t get back into China. They told me that I have to buy a tourist L so I can get back in. Does this Tourist L void my Z type? I still have 20 days left on my Z type, but only 4 more on the tourist L?