Code of Canon Law:
Can. 1248 §1. A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass.
Attending any Mass fulfills the obligation to attend Mass. So if someone went to a funeral Mass on a holy day, they would still fulfill their holy day obligation.
And while the canons do not directly address the possibility of fulfilling two obligations with one Mass (e.g. a Sunday night Mass for both a Sunday obligation and a Monday holy day), canon lawyers overwhelmingly agree that one Mass only satisfies one obligation.
When traveling holy day laws get a bit more nuanced:
Can. 12 §3. Laws established for a particular territory bind those for whom they were issued as well as those who have a domicile or quasi-domicile there and who at the same time are actually residing there…
What this canon means is that we are obligated to follow the rules of the diocese in which we actually live (domicile) or are staying in for a minimum of 3 months (quasi-domicile). So as long as you are in a different diocese for less than 3 months then you would follow the laws of your home diocese.
So if your home diocese celebrates the Assumption on Aug 15 then you should attend Mass wherever you are on Aug 15 even if the diocese you are visiting does not. It does not matter that it is a regular daily Mass.
However, finding a daily Mass to attend when traveling can be a bit problematic and the Church does not expect heroic efforts to find a Mass, just a reasonable effort.
Since you were unaware of this, you obviously do not have culpability for missing Mass.