Apple tree polination

I got 1 apple from my fiesta apple tree this year after the birds destroyed the rest , inside the apple was only one big seed the rest was either tiny seed our nothing , I had another breed of apple could it be that the one seed that developed was because it was cross pollinated ? Ps I know fiesta is partly self fertile just curious If it was crosspolinated our did it self polinate as would let me know if insects are going from tree to tree our not , and would like to plant the seed if it was a cross pollnation and see what I get from apple seed lottery

 

You will never know with apples and it will take years for it to fruit if it does.