The dumbest solution to the problem

dumbest.R

long <- data.frame(c("foo","qux","baz","quux"),c("baz","bar","foo","corge"))
shrt <- data.frame(c("foo","bar","baz"),c("baz","bar","foo"))

concatDumb <- function(data) {
  listed <- sapply(data, function(x) {
    # concatenate the character vectors to use substring matching
    paste0('$', paste(unname(x), collapse = '$'), '$')
  })
  return(unname(listed))
}

compDumb <- function(short, long) {
  # use pmatch to avoid odd behavior for duplicate matches
  matches <- !is.na(pmatch(concatDumb(short), concatDumb(long)))
  if(any(matches)) {
    # always return a data frame
    return(long[, matches, drop = FALSE])
  } else {
    print('No matches')
  }
}

compDumb(shrt, long)