The last vet to work on Nerd bird sent me a card too way back when. It did the same to me but it was a really nice gesture and I think most of the techs singed it. The time before when she worked on him he started biting her when she tried to retrieve him from his cage but the last visit she remembered him and said he was a sweet heart. I guess she remembered how once he was not being grabbed he ran up my arm and hid behind my neck while we talked.
I'm sorry the card made you cry. My vet too sent a card with a handwritten note and signed. I still have it. I worked for a vet for a few months and trust me they really do care. Its heart breaking for the staff to lose a loved one. We have to pull their files and send out a card. Time will heal, it just will take some time.