Once Lovestruck Beast is attacking, it'll remain attacking even if you no longer control a 1/1 creature.
Lovestruck Beast // Heart's Desire
If an effect copies an Adventure spell, that copy is exiled as it resolves. It ceases to exist as a state-based action; it's not possible to cast the copy as a permanent.
If an adventurer card ends up in exile for any other reason than by exiling itself while resolving, it won't give you permission to cast it as a permanent spell.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Kev Walker
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
