If you didn't create a keypair, you probably do not have one.
SSH2 traffic is encrypted with a symmetric session key established using DH, ECDH algorithms or GSSAPI key exchange. Neither the host key nor the user key are used for encrypting data – their only purpose is authentication.
Now remember that SSH supports several authentication methods: in addition to
publickey, almost all servers accept the simple
keyboard-interactive, in which no key generation or usage takes place – the password is simply sent to the remote server for verification.
In other words, "since I've already established ssh connections before, they must be somewhere" is incorrect – the user keypair is not necessary for establishing connections.
If you did create a keypair, it will likely be in
~/.ssh/id_* – for example,
id_rsa for the default RSA keypair,
id_ecdsa for ECDSA,
id_dsa for DSA. Although these files contain both private and public parts of the keypair, the public part is usually automatically extracted into a separate
id_*.pub file for convenience (
id_rsa and so on).