Isn't any more difficult than speechless in the third person.
You change the first person focus of attention from the conversation to something else; internal monolog, remembering to breath, the bootstrap sequence for the character's social function emulator, or whatever is appropriate to the character, and then you have them observe detail relating to the other party in the conversation that indicates that they were out of it for a significant, noticable span of time when their attention shifts back to the conversation.
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From: (Anonymous)
Speecheless in the first person
You change the first person focus of attention from the conversation to something else; internal monolog, remembering to breath, the bootstrap sequence for the character's social function emulator, or whatever is appropriate to the character, and then you have them observe detail relating to the other party in the conversation that indicates that they were out of it for a significant, noticable span of time when their attention shifts back to the conversation.
Pas de problem.