Hi Tyorr-- very glad to read that you saw this coming and acted accordingly... sorry about your clothes though. Street theft is unfortunatetly an issue in Buenos Aires, and most targets are visitors. This is a sad situation and I cannot apologize enough to those that come to our city to spend their leisure time and have to sometimes face these issues. The spraying of mud or mustard or ketchup is one of the oldest tricks in the book, but it is still used by these crooks to try to throw you off guard.
Kudos to you for seeing it coming, and I hope you can solve the stains with professional drycleaning.