I have discovered over the years of Tetra keeping that some species seem to have a hard time being captured and bagged. Some like the Garnet Tetras and Rummynose Tetras will try to play dead.
One thing that I 've found worked was to purchase hardier specimens of a similar species.
For example when purchasing a pair of Garnet or Pretty Tetras I would also purchase a pair of Head and Taillight Tetras for Cardinal Tetras I would purchase a pair of Neon Tetras or Glowlight Tetras. Or I would purchse fish that are naturally found together in the wild like Cardinal Tetras, Tubenose Pencilfish and Marbled and Blackwinged Hatchefish or Glass Bloodfins, Silver Hatchetfish, Three lined Pencilfish and Neon Tetras.
Here are a list of species below that are hard species to transport:
Pretty or Garnet or Black Wedged Tetras
Common Rummynose Tetras
False Rummynose Tetras
Three Lined Pencilfish
Other Pencilfish species
Now here are some more species that I would pair up with these hard Species:
Cardinal Tetras, False Neon Tetras with Glowlight Tetras, Neon Tetras and Umber Tetras and Rummynose species.
Garnet Tetras and Green Neons or known by Neon Costellos with Diamond, Lemon, Black Neon, Red eye Tetras or with Head and Taillight Tetras.
Black Neon Tetras and Flag Tetras can be transported with, Brass Tetras, Silver Tip Tetras, and Blue
Or Flag Tetras with black Neons.
Belfork's Pencilfish with Tubenose PencilFish and Black Neons or Black Lined Penguin Tetras.
Silver Hatchetfish with Glass bloodfins
Bloodfins with Green Fire Tetras
Red Phantom Tetras with Serpae Tetras, flame tetras and Black Phantom Tetras
Common Rummynose with Sivertip Tetras, False Rummynose and True Rummynose tetras.
Emperor Tetras with Tubenose Pencilfish and or Black Neon Tetras and Marble Hatchetfish.
Robert's Tetras with Greater and Lesser Bleeding Heart, Rosy and Serpae Tetras.
Spottted Headstanders with Striped or Marbled headstanders
When I purchase them together These finicky species feel more at home and tend to survive more