How to get the data back
When you look at your code, then you got get_option( "taxonomy_{$t_id}" ) in it, which actually calls the value from the DB options table. So you should simply replace the $t_id with your actual term id.
The term ID can be retrieved via
get_query_var( 'tag_id' )for Tags on tag archive pagesget_query_var( 'cat' )for Categories on cat archive pagesget_term_by( 'slug', get_query_var( 'term' ), get_query_var( 'taxonomy' ) )->term_idfor custom taxonomy and post format pages.
Why it is NOT recommended to do this!
You’re saving one additional entry in your DB options table per tag/term/category/taxon.
This means with a growing number of taxonomy terms, tags or categories, you’re quickly polluting your table with stuff that doesn’t belong there. Its also not recommended to prefix custom stuff with a generic name like taxonomy_. Try to find this again, when you don’t need it anymore. There’s also a high risk, that you may catch stuff that doesn’t belong to your custom “solution”. Always! use a proper prefix like wpse38656_ for DB entries.