Two fixes - one for the moment, one for the habit.
The moment: if it's only drifted a degree or two below working temperature, you have NOT lost the temper - the crystals are fine, the chocolate is just cold. 4-5 seconds in the microwave, stir well, check the temperature, repeat gently if needed. Tiny bumps only... a long blast takes you past the working window, kills the crystals, and THEN it's a full re-temper.
The habit: reverse your sequence. Moulds polished, sheets laid, scrapers ready, fillings at room temp - ALL of it before the tempering starts. Tempered chocolate is the impatient guest at the party; everything else waits for IT, never the reverse. Working in an AC room also slows the drift usefully.
Prep first, temper last, bump gently when needed. The thickened-bowl frustration disappears from your life 🙂
