dsm() translated in previous request will not be editable

Yes, that's why it was weird. I was looking at the word and typing it in, in correct case or any case, and still the search was empty.

In the meantime I imported a .po file of one module I translated using Gtranslator, and now those strings I couldn't find before are there (they aren't from the module I translated using Gtranslator.) I don't know if this had anything to do with it, just thought it was worth mentioning.

I'll report if I encounter more cases.

Happened again. Using the module Signup I get a notification message after I apply for an event. The text is in t() within the module, but it doesn't appear in l10n client, even when I can see it on the screen and having l10n opened while I'm applying.

This is the part from signup.module that wouldn't appear

    // Figure out if confirmation or reminder emails will be sent and
    // inform the user.
    $confirmation_email = $node->signup_send_confirmation ? '  '. t('A confirmation email will be sent shortly containing further information about this %node_type.', array('%node_type' => node_get_types('name', $node->type))) : '';
    $reminder_email = $node->signup_send_reminder ? '  '. t('A reminder email will be sent !number !days before the %node_type.', array('!number' => $node->signup_reminder_days_before, '!days' => format_plural($node->signup_reminder_days_before, 'day', 'days'), '%node_type' => node_get_types('name', $node->type))) : '';

So this text that appears in the drupal message isn't user customizable, but it informs user about sending emails (which are customizable).