Getting a new Visa after overstay

Hi, I overstayed in China, unfortunate circumstances, my passport and wallet were stolen, and I had to wait up to 4 weeks for my new passport to arrive from the British Embassy, and of course during this period my visa expired. I was told to go to immigration to sort this out, I did, paid the fine, and was told to re-apply for a new one in HK. I was given a temporary 10 day one. I decided to go home as that was the easier option, and I had enough of China at that point. Its been 2 years later, I was offered an internship in mainland, but when I went to apply for it, I was told that I need an invitation letter, is this a customary procedure, or am I just banned for 10 years, or is there some sort of appeal process?
Any advice or suggestions would be much appreciated, as the laws have just recently changed?