"Gladiolus flowers mean remembrance.

Today was really nice, I had a fun time with you guys! Thanks for giving me the tickets and unforgettable memories too."

"Dear you,

I had a really fun time too. Thank you again for the flowers, they're lovely! Remember to check the post-it and I hope we can spend time together again someday!

With love, Hoseok "

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Just to clarify, you left the note when you left the place. Probably gave it to a staff member to pass it to hoseok. So the note was given right before you totally left the place.