Edit: Resolution as an answer.
I entered Mexico nearly one month ago on a bus crossing from TX to MX. I crossed at around 2am and never was it directed or suggested to handle my immigration paperwork at that time. I was confused and anxious about entering Mexico and how the next few weeks would play out so neither did I ask nor check that I had done what was needed. After just a 10 minute wait I hopped on my next bus which took me to San Luis Potosi and later to Mexico City.
I stayed in the city for a few days, spent a week in Guanajuato then took a long night bus to Oaxaca city. Never was I stopped by immigration or reminded of the necessity of a visa until I arrived at a coastal town where my uncle lives. I told him about my crossing and he immediately realized that I didn't have a stamp or visa and was surprised I had made it all the way to Oaxaca without being stopped.
I have a flight from Mexico and a family wedding in two weeks so my uncle has suggested I cross into Guatemala to try to get exit and re-entry information so that I may then take my flight from Cancun.
I am currently in San Cristobal de Las Casas, less than a day's travel from most crossing points and want to handle this within a couple of days so that I can get this mistake behind me and ensure it does not affect my departure plans. Should I go straight to the large crossing city of Tapachula to handle this or a smaller, less touristed area. Do you have any suggestions as to how I should present this to the officials? Ideas about what I might expect as a response?
My spanish is pretty functional and I should be able to get across what happened.
Thanks a bunch, I appreciate any thoughts!