In a number of shuls as well as in a Bet Midrash, I have frequently seen someone who arrives after the services have finished say the beginning of the Amidah aloud until after the Kedusha (i.e. ending in Hakel Hakadosh).
Is there a requirement to hear / join in with Kedushah? What is the source for allowing a person to do his own "personal heicha Kedusha?
Wouldn't saying the Kedusha Desidra (aka Uva Letziyon) said near the end of Shacharit fulfill the obligation of someone who missed the Kedusha during the Amidah, anyway? If so, then what would be the need for someone to do this heicha Kedusha, or is this a mistake?