R 如何在观测缺失的地方添加零

以下是我拥有的一些数据的示例

 dput(df)
structure(list(ID = c("a", "b", "c", "d", "e", "f", "g", "h", 
"i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "b", 
"c", "d", "e", "f", "j", "k", "n", "m", "q", "r"), Number = c(1, 
2, 1, 3, 4, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 
1, 2, 1, 1, 1, 1, 1, 2, 2), Location = c(1, 1, 1, 1, 1, 1, 1, 
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 
2, 2, 2), Surveyor = c("JKK", "JKK", "JKK", "JKK", "JKK", "JKK", 
"JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", 
"JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK", 
"JKK", "JKK", "JKK", "JKK", "JKK", "JKK", "JKK")), row.names = c(NA, 
-31L), spec = structure(list(cols = list(ID = structure(list(), class = c("collector_character", 
"collector")), Number = structure(list(), class = c("collector_double", 
"collector")), Location = structure(list(), class = c("collector_double", 
"collector")), Surveyor = structure(list(), class = c("collector_character", 
"collector"))), default = structure(list(), class = c("collector_guess", 
"collector")), delim = ","), class = "col_spec"), problems = <pointer: 0x00000253510611f0>, class = c("spec_tbl_df", 
"tbl_df", "tbl", "data.frame"))

在上面的例子中，我有col ID，它包含字母a—t(我的真实数据有其他字母代码)，在Location1中，所有这些代码都存在.Location2年，其中一些人失踪了.

我想在遗漏身份证的Number栏中加0.

我的真实数据有25个位置，所以理想情况下，我希望能够抓住ID的完整列表，并对照每个位置判断，并在缺少的地方添加0.

我试过tidyverse::mutate个case_when个，但我没有任何进展.感谢任何帮助.