I don't know what you mean by "ESCAPE '!' ".
That is not any standard SQL syntax.
The major players support LIKE ... ESCAPE all in the same way (PostgreSQL, Oracle, SQLite, MS SQL Server, MySQL, IBM DB2). This is a strong hint that it may be standardised. In fact, SQL-92 has it in Chapter 8.5, page 214:
8.5 <like predicate>
Specify a pattern-match comparison.
<like predicate> ::=
<match value> [ NOT ] LIKE <pattern>
[ ESCAPE <escape character> ]
<match value> ::= <character value expression>
<pattern> ::= <character value expression>
<escape character> ::= <character value expression>
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)