I think I accidentally stole my dog

July 4th 2003, (I was 10YO at the time) my parents found a teacup chihuahua sitting behind some bushes outside of my grandma's senior apartments. She was wearing a brown leather collar with no tags on it. They brought her inside and we gave her water and food and later brought her home. My parents said they would keep an eye out for lost dog posters. my parents never found any. we named her Freedom, but we called her freedo. freedo quickly bonded to me and we became very close. Many times in my life she was my only friend. fast forward to 2016, she is starting to get very sick. I took her to the vet where they did an xray on her and we found out she has some heart issues.. but the vet also pointed out her chip. a chip i had no clue she had. i didnt know chips even existed in 2003. I honestly said nothing because at that point I had her for so long and she was near the end of her life. she passed in November of 2016 and it was extremely difficult for me. I do feel guilty that my parents never thought to take her somewhere to see if she had a chip tho. but im also thankfull for the time i had with her. she was everything to me.