So I guess you do not have a Backup before you make the “tweak” or you would not ask help here.
Also you do not remember what or how many “tweak”?
What was the Theme before the “tweak”?
English expression “needle in a haystack” but if you want you can send me XML file and I will look for you - to do this:
Menu ->Appearance ->Themes ->With current Theme selected ->Advanced ->Save current Theme as…
ZIP the file and send directly to address below.
Apart from this I can not help you more; may be someone else can.