Departing Schipol one evening we were levelling at FL230, only just as we began to level off we saw 'pop up' traffic level at FL240 in our 3 o'clock.
We triggered an RA in the other aircraft, but we only got a TA, thus we made no call to ATC. AMS did call us to confirm our clearance as FL230, which we did, and we were then promptly handed over to a different sector.
Just because you had an RA does not mean that the other a/c did as well.