Broken spark plug: Small piece of ceramic missing. Did I vacuum it out or is it in the cylinder?

Citroen C2 1.4l 54 kw VTR 2005, engine KFV

I changed my spark plugs today and one of them snapped while unscrewing. It was a relatively clean break, but after finally getting the bottom part out using a vacuum cleaner I somehow extended with a smaller piece, I noticed a small piece of ceramic is missing.The piece is roughly the size of a grain of rice, but very thin (about 0.5 mm thick). I'm not sure if the piston was at the top or bottom of the stroke when it happened.How likely is it that the vacuum caught it versus it falling into the cylinder? And if it's in there, how much damage could such a small, thin piece cause?

After putting everything back together, I started the engine. It ran very roughly at idle and kept almost stalling until it finally died after about 2 minutes. I suspect this is due to a faulty ignition coil (which I’m replacing tomorrow), but now I'm worried the ceramic piece might be the cause.