Make sure that you entered your transaction hash correctly in the Blockchain.info search field. Please note that if your transaction id is a URL like this:
https://blockchain.info/tx/9593513fc20fe356c7eca3e152f8722de3a0128c805466af05caa05237564f5a
then what you need to enter in the search field is its hash only, that is:
9593513fc20fe356c7eca3e152f8722de3a0128c805466af05caa05237564f5a
Sometimes there is a problem in the Blockchain.info network so your Bitcoin transaction status can not be found. When this happens, try using another block explorer like:
Blockcypher.com
Blockexplorer.com
Blockr.io
Blocktrail.com
Bitcoinchain.com
Copy your hash (hash only, not link transaction ID) in the search field available on the block explorer site. You can also search by Bitcoin address used.