I admit I did forget about that specific incident.

However, Dumbledore going cell to cell in Azkaban and Lord Voldemort attempting to subvert a prophecy predicting the end of the world in a fixed, controlled location seem like two very different things from a reader perspective.

It is also implied that Dumbledore did sense Harry's magic - at least on some level.

...the strongest had only as much magic left as a first-year child.

But he dismisses this because he is looking for a wizard strong enough to break into Azkaban and free Bellatrix Black. Lord Voldemort on the other hand, should be immediately and unconditionally suspicious of any and all magic he senses from Harry Potter.