Search text for a prefix and list all its suffixes in the text
R, 63 bytes



function(s,p,z=el(strsplit(s,' ')))sub(p,'',z[startsWith(z,p)])


Try it online!

The positive-lookbehind implementation is unfortunately 5 bytes longer due to the huge regmatches/gregexpr combination :

function(s,p)regmatches(s,gregexpr(paste0('(?&lt;=',p,')[^ ]*'),s,,T))