When it's returned you could add this line:
loanin date returned goes here
Then if you wanted to see which albums haven't been returned yet you
could go to the Report Writer and enter for Albums Filter Expression:
contains(notes,"loanout") and not contains(notes,"loanin")
If the same album was returned and loaned out again you would enter the new loan info in the loanout line and delete the loanin line at that point.
Of course, you could call loanout and loanin something else so long as you are consistant.