What made Colm feel vaguely sad despite his exciting discovery?

Colm felt vaguely sad despite his exciting discovery because it highlighted the fleeting nature of moments and connections he cherished. The realization that such discoveries often come with a sense of loss or nostalgia made him reflect on what he might be leaving behind. Additionally, the excitement was tinged with a sense of isolation, as the thrill of discovery was not shared with anyone else, deepening his feelings of loneliness.