I was recently granted Schengen visa (single entry) . After my stay, when leaving the Schengen area my flight was rebooked to the next day. So I technically had no where to go that night. German authorities in Frankfurt granted me re-entry despite having a single entry visa (apparently they made an exception) and made two diagonal line on the corner of my exit stamp 11.07. When leaving the next day, the guard was asking me questions about my situation and asked me to show him flight itineraries . After explaining the situation he stamped me exit and made two diagonal lines on the re-entry stamp (with an annotation below it but i don’t know what does it mean)
I’m afraid this would affect my future visa applications despite that I had no control over flight delays/cancellations. I would appreciate any support or explanations!