Bytea data values are handled as R raw types by the R environment. However, note that the read.table() function uses the number symbol ("#") as a comment character and hence data after "#" is truncated. One way to avoid the truncation when reading bytea values using read.table() is to turn off the interpretation of comment characters as shown in the this example:
frame<-try(read.table(IN,header=FALSE,sep="\t",quote="",nrows=1,comment.char=""),silent=TRUE)