set.seed(1)
x <- data.frame(c(1:10),rnorm(10,10, sd = 2.5))
colnames(x) <- c("id", "value")

   id     value
1   1  8.433865
2   2 10.459108
3   3  7.910928
4   4 13.988202
5   5 10.823769
6   6  7.948829
7   7 11.218573
8   8 11.845812
9   9 11.439453
10 10  9.236529

# Let's lose data
(x <-  x[-5,])

f <- function(x, fill_value){
  # Get number of rows
  n <- nrow(x)
  max_id <- max(x$id)

  # Get missing data position
  no_data_position <-  which(!(1:max_id %in% x$id))

  # Fill missing data
  out <- data.frame()
  start <-  0
  counter <- 1

  for(i in 1:max_id){
    if(!i %in% no_data_position){
      out[start + i, "id"] <- start + i
      out[start + i, "value"] <- x$value[counter]
      counter <- counter + 1
    } else {
      out[start + i, "id"] <- start + i
      out[start + i, "value"] <- fill_value
    }
  }
  return(out)
}


f(x, NA)

   id     value
1   1  8.433865
2   2 10.459108
3   3  7.910928
4   4 13.988202
5   5        NA
6   6  7.948829
7   7 11.218573
8   8 11.845812
9   9 11.439453
10 10  9.236529