Answer: Two of the mostly widely plants spring-blooming rock garden plants are Saponaria ocymoides (Bouncing Bet) and Cephalophyllum (ice plant). When these plants are in full bloom it's difficult to see the foliage. Flowers are daisy-shaped on both. Ice plant foliage is succulent and 3-sided; foliage on Saponaria is dark green, long and narrow.
Hope this sheds some light on the possibile identities of the plants you saw!
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