Linda... I think you had a typo.... There are over 77,000 registered daylilies, not 7,000. Thousands of new ones are added each year.
Unless you know the hybridizer, where it was purchased or there is some really unusual thing about the bloom, it is nearly impossible to know, for sure, what an unknown daylily is.
We can ** guess ** but it is just a guess.
Yes, knowing size of bloom, height of scape, and any other information can help to ID. Such as do you know how old it might be? Is it an early or late season bloomer?